Boy Meets World has a surprisingly high implicit body count. For whatever reason, a character’s final appearance of a season has a fairly strong tendency to include them being in mortal peril, whether comic or dramatic, and then the character doesn’t always return for the next season.
Example: Stuart Minkus is the nerdy kid in season 1. In the final episode, an over-the-credits scene sees Cory and Shawn harnessing their latent psychic powers to blink him out of existence. It’s clearly meant to be a non-canon credits gag, but Minkus is totally absent starting season 2, so apparently our heroes legit killed a guy with their mind powers.
Example 2: Mr. Turner is in a motorcycle wreck during a very special episode towards the end of season 4. We last see him badly injured in a hospital bed, giving Shawn’s hand a weak but reassuring squeeze. This is meant to indicate that he’s gonna be okay, except that when I say “we last see him” I don’t mean “for the episode” or even “for the season,” I mean for the entire rest of the series. And there’s a whole other season that takes place in high school, so it’s not just that the cast left him behind but in good health when they graduated. Dude is gone.
I’m kind of lying, though, because the show’s writers seem to have noticed the problem in a late season 5 episode where Minkus does reappear, claiming to have been in an off-camera “other part of the school” for the past four years, and calls out to an off-camera Mr. Turner. Mr. Turner doesn’t respond, partly because actor Anthony Tyler Quinn wasn’t actually on set and partly because he died a year ago and Minkus is having a psychotic breakdown after being trapped in a psychic mirror dimension for four years by Cory and Shawn’s powers.
A similar author saving throw was made to save the most prominent of the not one, not two, but three siblings mysteriously erased from existence after season 1. Cory’s younger sister, the only one of the three to be Cory’s sibling, specifically, and the only one to appear in more than one episode is also the only one to be returned to existence after a season 2 obliteration. She came back under a new actor in season 3, so we can be reasonably confident she isn’t dead, but probably shouldn’t rule out the possibility that the Matthews family’s daughter was replaced by an only moderately convincing changeling, something that might seem farfetched until you remember that Cory and Shawn once vaporized someone with psychic powers on camera and also that the sibling in question’s name is Morgan, as in “le Fey.” The possibility implied by canon is that season 1 Morgan and season 3 Morgan are the same person, but that she was grounded for an entire year so thoroughly that she did not once see Cory during that time, which is probably darker than the changeling theory, all things considered.