Professor Oak (anime)

Professor Samuel Oak オーキド・ユキナリ博士 Dr. Yukinari Okido
Professor Oak in Pokémon Journeys: The Series
Gender	Male
Eye color	Black (before Sun & Moon series) Brown (Sun & Moon series onwards) Blue (as a child)
Hair color	Gray (currently) Brown (as a child)
Hometown	Pallet Town
Region	Kanto
Relatives	Gary Oak (grandson) Samson Oak (cousin) May Oak (granddaughter; EToP only) Unnamed father (EToP) Unnamed mother (M04) Mayor of Pallet Town (brother)
Trainer class	Former Trainer, Watcher, Professor
Game counterpart	Professor Oak
Animated debut	Pokémon - I Choose You!
English voice actor	Stuart Zagnit (originally credited as Stan Hart) (EP001-AG133) Carter Cathcart (AG176-JN147) (MoMP) Tara Jayne (child; M04)
Japanese voice actor	Unshō Ishizuka (EP001-SM048) Kenyu Horiuchi (SM111-JN147) Keiko Toda (child; M04)

Professor Samuel Oak (Japanese: オーキド・ユキナリ博士 Dr. Yukinari Okido) is a Pokémon Professor and a major supporting character of Pokémon the Series who lives and works at his research lab in Pallet Town. He appears semi-regularly to give Ash Ketchum advice to help him achieve his goal of becoming the greatest Pokémon Master.

In addition to his role in the animated series, he also appears in bonus segments exclusive to the Japanese versions, where he hosts various informative lectures: Pokémon Lecture, Big Pokémon Encyclopedia, Big Pokémon Examination, Pokémon Live Caster, and Pokémon Holo Caster.

In animation

Pokémon the Series

History

Pre-series

In Will the Real Oak Please Stand Up?, Professor Oak mentioned that his childhood nickname was "Flying Finger Sammy" because he was particularly good at playing video games.

At some point, Oak was a lecturer at Celadon University, where Foster was one of his top students. In Professor Elm's debut, he mentioned that he was one of Oak's top performing students at the university. In Spell of the Unown: Entei, it was revealed that Oak also taught Spencer Hale and Ash's mother Delia.

In Fossil Fools, Professor Oak mentioned that he decided to become a Pokémon Professor after seeing the fossil of an Omanyte shell during a museum visit.

Four years before the start of the series, Professor Oak hosted a Pokémon Summer Camp, where he lectured the many attendees including Goh and Chloe about Pokémon. After hearing about Goh and Chloe's encounter with an unknown Pokémon, Oak told them the Pokémon they saw was most likely the Mythical Pokémon Mew, inspiring Goh to catch Mew one day. Some time later, he would host another camp, which was attended by Ash and Serena.

Pokémon the Series: The Beginning

Professor Oak debuted in Pokémon, I Choose You!, appearing on a late night television show explaining the three first partner Pokémon that Pokémon Trainers would receive. The next day, three Trainers from Pallet Town, including his grandson, Gary Oak, came to his lab, ready to become Pokémon Trainers. Oak gave them each a first partner Pokémon, including giving Gary his Squirtle, though this wasn't revealed until much later in the series. Later that same day, Ash came to him as he was also starting his Pokémon journey and needed his first Pokémon. But because he was so late, the only Pokémon that Oak had left was a rebellious Pikachu.

In Pokémon Emergency, Oak called the Viridian City Pokémon Center after hearing that Ash had already made it there from his mother. He stated how he was surprised that he had made it that far, and expressed doubts he had when Ash first left. Mentioning making a bet of a million dollars with Gary that Ash hadn't captured any new Pokémon, he was disappointed to hear that this was indeed true and he had lost the bet with his grandson. When Ash told him that he had seen an unknown Pokémon, which resembled the stone carving above him, he waved it away as nonsense, saying that Trainers have searched their whole lives for that Pokémon, and none have succeeded.

Professor Oak and his grandson

Over the course of Ash and Gary's journeys, Professor Oak took care of the Pokémon they captured that were sent to his lab. He would often gloat about how much farther ahead his grandson was to Ash like in Mystery at the Lighthouse, which often caused Ash to be extra competitive. During the Indigo Plateau Conference, Oak became greatly disappointed when he discovered that Gary had lost in the third round, but decided to look on the bright side, telling Misty and Brock that it would do Gary good to see "every road has a few bumps along the way." He had arrived with Ash's mother with the goal of cheering Ash on in mind.

Following the Indigo Plateau Conference, Professor Oak asked Ash to pick up a mysterious Poké Ball from his friend, Professor Ivy, who lives on Valencia Island in the Orange Islands. He wasn't at all surprised when Ash called him asking if he could compete in the Orange League. Though he wanted to study the GS Ball, he also wanted Ash to compete in the league so that he can get more training. During Ash's adventures in the Orange Islands, he befriended a Pokémon Watcher by the name of Tracey Sketchit who was a great admirer of Professor Oak. When the group returned to Pallet Town in The Rivalry Revival, Tracey asked if he could become his assistant, which Oak graciously accepted.

Pokémon the Series: Gold and Silver

Not being able to discover the mystery behind the GS Ball, Professor Oak called for Ash's assistance once more and asked him to travel to the Johto region and give the Ball to his friend Kurt. He also explained that there were many new Pokémon out west which made Ash all the more eager to go and catch up with his rival, Gary. Ash completed this task in Going Apricorn!, leaving the GS Ball in Kurt's possession for further study.

In Will the Real Oak Please Stand Up?, Oak and his friend DJ Mary announced they were going to broadcast a live show in Maroon Town. Team Rocket got wind of this and disguised themselves as Oak and Mary. With the help of Nurse Joy, a quiz show determined who was the real Oak and Mary.

In Hatch Me If You Can, Professor Oak and Delia traveled to New Bark Town to catch up with Professor Elm, and also to see Ash before the upcoming Silver Conference. The trio's dinner plans were interrupted after a nearby Pokémon Center alerted them to an issue with Ash's newly hatched Larvitar. Oak and Elm were then able to stabilize Larvitar's body temperature.

Professor Oak, along with Delia, traveled to Silver Town to watch Ash and his grandson Gary compete in the Silver League Conference, from A Claim to Flame! to Johto Photo Finish.

After learning Ash was traveling to the Hoenn region, Professor Oak gave him an updated Pokédex and wished him the best of luck.

Pokémon the Series: Ruby and Sapphire

In Gonna Rule the School, Oak was lecturing the students of Rustboro's Pokémon Trainers' School via satellite.

Oak traveled to Hoenn in A Six Pack Attack! to meet with Professor Birch for the first time and brought along the Kanto first partner Pokémon as they interacted with the Hoenn first partner Pokémon. Max was particularly excited to meet his idol in person, but the meeting was interrupted when Team Rocket kidnapped both the Hoenn and Kanto first partner Pokémon. Oak, May, and Max followed Team Rocket to their cave headquarters and later worked together to escape the facility with the first partner Pokémon.

In The Right Place and The Right Mime, Professor Oak noticed that one of his Squirtle felt most comfortable being with May, and offered it for her to raise into a strong Pokémon. He also agreed to look after her Bulbasaur after seeing that it was interested in learning from Ash's own Bulbasaur.

In The Unbeatable Lightness of Seeing!, when Ash was still recovering from his defeat at the Battle Pyramid, Professor Oak brought him a special package meant to cheer him up, containing a poster with the prints of his Pokémon, a fishing lure from Misty, and food from his mother. He also handed Ash a postcard from Gary and told him that his grandson was doing research in the Sinnoh region and that many Pokémon who live there cannot be found anywhere else. Later, he was asked to judge the impromptu Contest Battle between May and Drew. Along with Scott, he judged their battle, which ended in a victory for Drew after his Roselia and Butterfree knocked out May's Combusken and Skitty.

Pokémon the Series: Diamond and Pearl

Professor Oak in Pokémon the Series: Diamond and Pearl

Ash spoke to Professor Oak regularly over the phone while he traveled through the Sinnoh region. Dawn was able to recognize him from television, but it was because of his Pokémon poetry and not his research.

In Get Your Rotom Running!, Oak suggested that Ash and his friends should visit the Old Chateau to sample its famous delicacy, the Old Gateau.

Professor Oak in the Twinleaf Festival

In Strategy Begins at Home!, Ash called Professor Oak while staying at Johanna's house and said he would be training in Twinleaf Town for a while. Oak told him to use this opportunity to learn from Johanna, as her experience as a Top Coordinator could be helpful to him. Oak also announced that he would be attending the Twinleaf Festival as a special guest.

In A Faux Oak Finish!, he traveled to Sinnoh to give a lecture on "the interrelation of Pokémon and Evolution stones" on the first day of the Twinleaf Festival. However, on his way to Twinleaf Town, his car got a flat tire and forced him to make a stop near a marshland. While the driver was replacing the tire, Oak decided to explore the area. He found a group of wild Pokémon who led him to a cave where a depressed Lombre was hiding. Oak found out why Lombre was so sad and gave it a Water Stone, allowing it to evolve into Ludicolo and immediately taking it out of its depressed state.

Meanwhile, in Twinleaf, James was in the town's auditorium disguised as Oak plotting to steal all of the attendees' Pokémon. When Oak arrived there, everyone in the auditorium looked confused as James insisted he was the real Professor Oak. Seeing this, a Trainer in the audience sent out his Tyranitar and asked for help, saying he was having trouble with the Armor Pokémon. James failed to figure out what was the cause of the problem and was sent blasting off by Tyranitar, but Oak was able to help the Pokémon by removing a thorn from its foot. After that, Professor Oak proceeded to give his lecture.

Pokémon the Series: Black & White

Professor Oak in Pokémon the Series: Black & White

Professor Oak was given a major redesign in Pokémon the Series: Black & White, using a different shirt collar style and wearing his lab coat above it. His hairstyle also changed, becoming more boxy. These changes make his look closely resemble his most recent game counterpart artwork.

Oak made plans to travel to the Unova region to meet with his friend, Professor Juniper, in In The Shadow of Zekrom! and invited Delia and Ash to go with him. He had since returned to Kanto as seen in Crisis from the Underground Up!, where Ash called his laboratory from Nimbasa City.

In New Places... Familiar Faces!, Ash called Professor Oak to inform about his loss at the Vertress Conference. In The Fires of a Red-Hot Reunion!, the Professor appeared again in a video lecture about the Kanto first partner Pokémon that was presented at the Kanto Fair, accompanied by Tracey. Later, Ash's Charizard came to his lab from the Charicific Valley so Ash would switch him for his Unfezant. Oak liked the idea of Unfezant being with him, as she could make good friends with Ash's Swellow and Staraptor.

Professor Oak catching a Rotom

In To Catch a Rotom!, he appeared in the Decolore Islands, having traveled to Torom Island. Professor Oak wished to capture a Rotom to study, and eventually succeeded after helping Ash and his friends defeat Team Rocket.

As seen in Butterfree and Me!, Professor Juniper sent Ash's Pokémon caught in Unova to Oak's laboratory. Ash contacted Oak to send Leavanny to him in order to help a Caterpie evolve.

In The Dream Continues! Professor Oak was interviewed by Alexa, a reporter from the Kalos region which gave him a chance to see Pokémon from there much to his delight. He was later present when Ash announced his intention to return with Alexa to Kalos to challenge its league. As usual, Professor Oak was entrusted with the care of the Pokémon Ash had caught in Unova, as well as Charizard who would be remaining at the lab permanently from then on.

Pokémon the Series: XY

In A Battle of Aerial Mobility!, Professor Oak was introduced to Froakie before being shocked by Rotom.

He was later mentioned in Battling on Thin Ice!, where it was revealed that Ash and Serena both attended his Pokémon Summer Camp during their childhood.

In Till We Compete Again!, he joined in on a video call with Delia to Ash and his friends, where he learned Ash was going to return to Pallet Town later that day.

Pokémon the Series: Sun & Moon

Professor Oak in Pokémon the Series: Sun & Moon

After winning a trip to the Alola region, Delia and Ash headed to Professor Oak's lab, where he received Ash's on-hand Pokémon and took the opportunity to entrust Delia with a Pokémon Egg. He asked her to deliver the Egg to his cousin Samson Oak, at the Pokémon School on Melemele Island.

After meeting up with Delia in Alola to New Adventure!, Samson made a video call to Professor Oak and notified him the Egg arrived safely. Professor Oak did not tell Ash what Pokémon it was, so only after hatching in Getting to Know You! was it revealed to be a Vulpix, which Samson kept.

Professor Oak and his cousin Samson Oak

In Alola, Kanto!, Ash, his classmates, Samson, and Professor Kukui, who were all visiting Kanto, arrived at his lab to examine the differences between Kantonian and Alolan Pokémon. He appeared briefly in When Regions Collide! to see Kukui and his students fly back to the Alola region.

Professor Oak appeared on television in Night of a Thousand Poses!.

In Show Me the Metal!, Ash made contact with him after discovering a group of Meltan. Rotom sent through its gathered data for Oak to examine. In the following episode, Professor Oak informed Ash that he had identified the mysterious Pokémon as an entirely new species, and he settled on the name "Meltan", the Hex Nut Pokémon and gave it a Steel-type classification.

In Final Rivals!, Oak and Delia arrived at Manalo Stadium to watch Ash's battle during the Manalo Conference finals. Upon arriving, he met Ash's Meltan for the first time, then watched as it combined with the other Meltan to evolve into Melmetal. He was happy to witness Ash win the Malano Conference in the next episode. During the attack by the Guzzlord in Z-Move Showdown!, Oak was among the people that were being evacuated until another Guzzlord appeared, blocking the ships.

After the crisis had been resolved, Oak remained at Manalo Stadium to watch Ash and Professor Kukui's exhibition match. Following Ash's win, he and Delia returned to Pallet Town.

Pokémon Journeys: The Series

Professor Oak in Pokémon Journeys: The Series

In Legend? Go! Friends? Go!, Professor Oak traveled to Vermilion City to assist in the opening of Cerise Laboratory and invited Ash to join him and attend the ceremony. He was later present when Ash and Goh recounted their encounter with Lugia. After Ash was appointed as one of Professor Cerise's research fellows, he and Delia returned to Pallet Town.

In Advice to Goh!, Professor Oak met Ash and Goh as they visited his laboratory. He was impressed by the number of Pokémon Goh had caught, especially his Suicune, and told him about Project Mew, recommending that he should join it. Goh was reluctant at first, but after meeting Gary and seeing how experienced he was, he changed his mind and decided to follow Professor Oak's recommendation.

He reappeared in Friends, Rivals, Lend Me Your Spirit! as Ash and Goh visited his laboratory again. During the visit, he watched the battle between Ash and Paul, as well as telling Ash and Goh that Paul had come to visit his laboratory due to Paul having been asked to become a Gym Leader and wanting to learn more about Pokémon.

In Battling as Hard as Stone!, Professor Oak was seen watching Ash's Masters Eight Tournament match against Steven alongside Delia, Tracey, and Ash's Pokémon. From Bewitch, Battle, and Bewilder! to Whittle While You Work!, they watched Ash's match against Cynthia.

In A Flood of Torrential Gains!, they watched Ash's match against Leon. Before the battle began, Professor Oak delivered a monologue about how proud he was of Ash. In Partners in Time!, they watched the awards ceremony taking place after Ash’s victory.

In Heroes Unite!, Professor Oak greets Ash as he returns to Pallet Town to congratulate him on his victory against Leon. In the following episode, Professor Oak attends a party taking place at Cerise Laboratory. Sometime later, he is seen being introduced to Horace by Gary.

In The Rainbow and the Pokémon Master!, Ash visits Professor Oak to see the first partner Pokémon that he’s giving away, only to learn that there was a Charmander missing. When Ash and Gary find Charmander, Professor Oak resumes his check-up on the first partner Pokémon.

Character

Professor Oak lives up the road from Delia Ketchum and her son, and he and Delia often appear together as good friends. His known relatives are his grandson Gary and his cousin Samson. He is also good friends with Professors Birch and Juniper.

His often-forgetful attitude and other antics are notorious. He also has a hobby of composing senryū, haiku-like poems about Pokémon or Pokémon-related themes.

In the novelizations written by Takeshi Shudō, Professor Oak comes from a prestigious family. He has two brothers, one of whom is the mayor of Pallet Town while the other is its postmaster, and his grandfather was the first Trainer from Pallet Town to receive widespread recognition, while Samuel himself gained prominence after he published a research paper on Pokémon at the age of 20. It is also stated that he became a professor at Celadon University at the age of 25. According to Professor Elm, Professor Oak's studies and research mostly focus on how humans and Pokémon interact with each other.

Pokémon

This listing is of Professor Oak's known Pokémon in Pokémon the Series:

On hand

Rotom

Status unknown

Pidgey

Voice actors
Debut	Will the Real Oak Please Stand Up?
Japanese	Katsuyuki Konishi
English	Katsuyuki Konishi

Professor Oak caught this Pidgey off-screen during Will the Real Oak Please Stand Up?, where he used it to get back the food that Team Rocket had stolen and then send them blasting off.

Pidgey's known moves are Quick Attack and Gust.

Dragonite

Voice actors
Debut	The Mastermind of Mirage Pokémon
Japanese	Katsuyuki Konishi
English	Katsuyuki Konishi

Professor Oak used his Dragonite to battle against the Mirage Mewtwo created by Dr. Yung along with Misty's Gyarados, May's Combusken, and Ash's Pikachu, but like the other Pokémon, it was defeated.

Dragonite's known moves are Twister, Hyper Beam, and Dragon Rage.

Temporary

Bulbasaur

Voice actors
Debut	Bulbasaur and the Hidden Village
Japanese	Megumi Hayashibara
English	Tara Jayne (EP010-AG133) Michele Knotz (AG189-present)

Main article: Ash's Bulbasaur

In Showdown at the Oak Corral, Professor Oak used Bulbasaur to help stop Butch and Cassidy from stealing the Pokémon at his lab.

Cyndaquil

Voice actors
Debut	Good 'Quil Hunting
Japanese	Yūji Ueda
English	Kayzie Rogers

Main article: Ash's Cyndaquil

In Showdown at the Oak Corral, Professor Oak used Cyndaquil to help stop Butch and Cassidy from stealing the Pokémon at his lab.

Totodile ♂

Voice actors
Debut	The Totodile Duel
Japanese	Chinami Nishimura
English	Kayzie Rogers

Main article: Ash's Totodile

In Showdown at the Oak Corral, Professor Oak used Totodile to help stop Butch and Cassidy from stealing the Pokémon at his lab.

Rotom

Debut	To Catch a Rotom!

In To Catch a Rotom!, Professor Oak used a wild Rotom in its Frost Rotom form to help defeat Team Rocket.

Rotom's known moves are Thunderbolt and Blizzard.

Dub only

Seaking

Debut	Putting the Air Back in Aerodactyl!

In the dubbed version of Putting the Air Back in Aerodactyl!, Professor Oak told Tracey that when he was a young Trainer, he owned a Seaking, which he met in a creek near Vermilion City.

None of Seaking's moves are known.

Various Pokémon are used in his lectures, which may belong to him or to Trainers whose Pokémon he cares for.

Gives to new Trainers

Bulbasaur

Debut	Pokémon - I Choose You!

Bulbasaur is a Pokémon that Professor Oak gives to new Trainers. Bulbasaur was mentioned in the first episode of the animated series, as one of the three first partner Pokémon new Trainers in Pallet Town can choose from. Ash dreamed of owning one, and it was his second choice of a first partner Pokémon, after Squirtle. However, when he arrived at Professor Oak's Laboratory, it was too late, as an unnamed Trainer who started the same day had already taken it.

In Journey to the Starting Line!, a new Trainer called Gilbert claimed a Bulbasaur. Another one appears in A Six Pack Attack!, where Oak shows them to Max. Suddenly, Team Rocket captures them along with the other Kanto and Hoenn first partner Pokémon. Max finds them and makes Bulbasaur and Treecko Tackle and Pound the bars away. It then helps send Team Rocket blasting off. Another one appears in The Right Place at the Right Mime! along with the other first partner Pokémon.

In The Rainbow and the Pokémon Master!, another Bulbasaur was seen performing some medical tests.

Various Bulbasaur's moves are Tackle and Vine Whip.

Charmander

Debut	Pokémon - I Choose You!

Charmander is a Pokémon that Professor Oak gives to new Trainers. Charmander was mentioned in the first episode of the animated series, as one of the three first partner Pokémon new Trainers in Pallet Town can choose from. Ash dreamed of owning one, although it was his last choice of a first partner Pokémon coming after Squirtle and Bulbasaur. However, when he arrived at Professor Oak's Laboratory, he found out it was too late, as another Trainer who started the same day had already taken it.

In Journey to the Starting Line!, Gilbert was intended to start his journey as a Pokémon Trainer, but the trio of Kanto first partner Pokémon were scared off when Ash's Tauros stampeded through Professor Oak's house. Professor Oak, Tracey, Delia and Gilbert split up in order to find the three missing Pokémon. The Charmander was the first one to be found.

Another one appears in A Six Pack Attack!, where Oak shows them to Max. Suddenly, Team Rocket captures them along with the other Kanto and Hoenn first partner Pokémon. Max is able to find them and then has Torchic and Charmander heat the cage with Ember until finally they are free. It then helps send Team Rocket blasting off. Another one appears in The Right Place at the Right Mime! along with the other first partner Pokémon.

In The Rainbow and the Pokémon Master!, a Charmander disappeared moments before performing some medical tests and Ash set out to look for it in the Lab. Ash found it trapped between some rocks and with Gary's help, they managed to rescue it.

Various Charmander's known moves are Ember.

Squirtle

Debut	Pokémon - I Choose You!

Squirtle is a Pokémon that Professor Oak gives to new Trainers. Squirtle was mentioned in the first episode of the animated series, as one of the three first partner Pokémon new Trainers in Pallet Town can choose from. Ash dreamed of owning one, and it was his first choice of a first partner Pokémon. However, when he arrived at Professor Oak's Laboratory, he found out it was too late, as another Trainer who started the same day had already taken it.

In Journey to the Starting Line!, a set of the three Kanto first partner Pokémon in which a boy named Gilbert was supposed to choose from as his starting Pokémon were scared off by Ash's Tauros. Professor Oak, Tracey, Delia, and Gilbert had to split up and find the three missing Pokémon. Squirtle was the second one found. The Tiny Turtle Pokémon was stuck in a tree that was hanging over a cliff. Ash's Bulbasaur managed to catch the Squirtle before it could fall off the cliff.

Another one appears in A Six Pack Attack!, where Oak shows them to Max. Suddenly, Team Rocket captures them along with the other Kanto and Hoenn first partner Pokémon. Max finds them and asks Mudkip and Squirtle to cool the bars with Water Gun which eventually frees them. It then helps send Team Rocket blasting off. Another one appears in The Right Place at the Right Mime! along with the other first partner Pokémon, in the end May claims Squirtle.

In The Rainbow and the Pokémon Master!, another Squirtle was seen performing some medical tests.

Various Squirtle's known moves are Tackle and Water Gun.

Gave away to Trainers

Gary's Squirtle

Ash's Pikachu ♂

Gilbert's Bulbasaur

May's Squirtle

Given away

Egg

Residing at his Lab

Krabby	Krabby → Kingler	Muk	Tauros (×30) ♂
Doduo → Dodrio	Snorlax	Heracross ♂	Noctowl
Bayleef ♀	Bulbasaur	Cyndaquil → Quilava	Totodile ♂
Phanpy → Donphan	Nidoking ♂	Nidoqueen ♀	Magmar
Scizor	Golem	Pinsir	Houndoom
Fearow	Alakazam	Skarmory	Kingdra
Torkoal	Glalie	Swellow	Sceptile
Corphish ♂	Staraptor	Torterra ♂	Infernape ♂
Buizel ♂	Gible ♂	Gliscor	Unfezant ♀
Leavanny ♂	Palpitoad ♂	Boldore	Krookodile ♂
Charizard ♂	Oshawott ♂	Pignite ♂	Snivy ♀
Scraggy ♂	Talonflame	Hawlucha ♂	Noivern ♂
Dragonite	Gengar	Lucario	Sirfetch'd
Dracovish	Pidgeot

Other

There are various Pokémon that live on the Oak Corral. Only a handful have been seen but there are various kinds of different Pokémon. People like Professor Oak and Tracey care for them. Other Trainers' Pokémon reside here such as Gary's.

Squirtle	Caterpie	Butterfree	Kakuna	Beedrill	Pidgey
Pidgeotto	Rattata	Raticate	Spearow	Raichu	Sandshrew
Sandslash	Nidoran♀	Nidoran♂	Ninetales	Oddish	Gloom
Vileplume	Paras	Parasect	Dugtrio	Alolan Dugtrio	Psyduck
Mankey	Primeape	Growlithe	Poliwag	Poliwhirl	Bellsprout
Weepinbell	Victreebel	Tentacool	Tentacruel	Geodude	Alolan Geodude
Ponyta	Rapidash	Slowpoke	Dodrio	Seel	Dewgong
Alolan Muk	Onix	Krabby	Voltorb	Electrode	Exeggcute
Exeggutor	Alolan Exeggutor	Marowak	Rhyhorn	Rhydon	Tangela
Horsea	Seadra	Goldeen	Seaking	Staryu	Starmie
Magikarp	Gyarados	Snorlax	Hoothoot	Quagsire	Hoppip
Skiploom	Jumpluff	Bellossom	Corsola	Taillow	Starly
Pidove

Previously resided at his Lab

Arcanine

Umbreon

Bulbasaur ♀

Aipom ♀

Past self

Spoiler warning: this article may contain major plot or ending details.

Sam

Main article: Sam

Oak appeared as a young boy, Sam (Japanese: ユキナリ Yukinari) in Celebi: The Voice of the Forest. Ash befriended the young Oak, who, because he time-traveled from 40 years in the past, was around the same age as Ash. The revelation that Sam is Oak, while inferred thanks to disclosure of Oak's first name in The Power of One, comes only at the end of the movie when Oak implicitly confirmed the connection through his knowledge of Sam's name despite Ash having never told him of it. Additionally, Tracey discovered the sketchbook in which young Sam drew Pikachu sleeping with Celebi in Oak's closet.

In the animated series, Oak never revealed or discussed Charmeleon, though his past as a Trainer was vaguely mentioned by Agatha in The Scheme Team.

Despite the fact that Sam saw many Generation II Pokémon throughout the movie (notably the Mythical Celebi and the Legendary Suicune), the Pokédex he gifts Ash in the Kanto arc only catalogs Generation I Pokémon, claiming that they were all the Pokémon that the world knows. This discrepancy is likely no longer canon, instead representing a silent retcon that occurred due to the ever-increasing number of Pokémon; indeed, Pokémon from Generation II, Generation III, and Generation IV are able to be trained in Kanto during the Generation I remakes FireRed and LeafGreen, as well as during the Generation II remakes HeartGold and SoulSilver. Perhaps to avoid a similar plothole, the number of Pokémon as of the current generation is no longer explicitly mentioned in animated series-related media.