From "Downtown as Fruits" to the theatrical movie.
Not the place for this, I know, but I have never, ever been a fan of Helga and Arnold together, and that the show gave itself over to her obsession (the correct word for this) in the latter half of its run made it a trial to watch, sometimes.
Not so much that as the fact that, after the 'very special episode', the character behaves like they always have, sometimes worse, leading one to wonder what the point was. And factoring episodes for the respective girls like "Ghost Bride" and "Homecoming Upset" into the mix just makes the whole 'this is why I'm so mean' thing seem, I dunno, shamelessly manipulative...but that's just my opinion.
I'm reminded of a "Simpsons" episode: "Some animals are just jerks." Again, just my opinion.