Goofs

When a vampire is staked and the weapon left in, it changes whether the weapon dusts when they do or not.

Throughout the early seasons, it's clear that the actors/actresses portraying teenagers are actually in their 20s . This is usually done to get around child labor laws, which won't allow teenagers to work full time on a set, due to interfering with their real-life schooling. Plus casting adults adds to the benefit of better acting from the actors/actresses due to having more experience, with the added advantage that the producers are able to sexualize the characters without consequences. Lastly, it gives the general viewing audience who are teenagers (or young people) someone they can look up to.

During most of the fight scenes, it's obvious in some shots, that the characters are not the main actors who play them, but their stunt doubles.

In nearly every episode presented in widescreen, there is crew/equipment visible and/or revealing mistakes. This is because the series was originally shot for 4:3 frame and these issues would not have been visible as the show was originally intended to be presented. As such, one should take much of the goofs reported on episodes as being conditional on applying only to the widescreen alternate version.