Song is "ABCDEFU cover by Our Last Night" and this thought occurred when I had a fate gacha reaction video on mind (sucks it's in Spanish but still had some good clips) here is the link. The part that put this in mind is at 22:45 (song was just me listening to it earlier)
Location: Imagine some Olympus looking place (think of an ancient city vacation spot for Chaldea) high up in the sky above the clouds like Olympus looks like yet oddly enough there is a giant cannon pointing towards the sky even higher and it just so happens to be loaded (no one really noticed it because it's off away from the city area)
People: Archer Emiya, Archer Emiya Alter, Saber Emiya (Shirou that merged with Muramasa but this one has Shirou in control like other fanfics) and Oath under snow Shirou (pretend he was summoned)
So, imagine the 4 Emiya's are going for a walk to relax (aka hide from the girls) and happened to stumble upon the cannon and go to inspect it and noticed its loaded and ready to fire into the sky but would do nothing to harm anything if fired and they noted handlebars on the cannonball. Thus, OUS Shirou suggests to firing the cannon while they also hold onto the bars and to have fun with it thus, they all did despite finding it to be stupid, but they decided to have fun and they get launched into the sky all the while they smile and laugh and since the ball is spinning they also spin and gain momentum and when the cannonball is about to begin its decent they release the handlebars and get launched higher into the sky all the while they still laugh aloud being viewed for all to see and hear down in the town which happens to be quite the lot of servants and the master.
Some servants thought that it was fun and would want to try it as well, others thought that it was stupid or dangerous, others were glad the 4 were having fun, some annoyed or concerned that they did that while others were just surprised.
At the end of the day the 4 Emiya's had a good time and decided to do things like that more often when they get the chance and aren't busy which is rare.

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My random Archer Emiya "crack fic moments"
HumorI had multiple occurrences of me thinking of random scenarios with Archer Emiya being at the center and decided to share these messed up but hilarious scenarios I thought of with you guys. Each "chapter" is just a different thought and the more I th...