I knew next to nothing about this episode when I watched it. It was out of pure luck that I did end up watching this one. But I was surprised at how good it was.
I haven't seen a ton of early KOTH episodes with Connie but in the ones I'd seen, she seemed a lot nicer, friendlier, and overall more likeable than the rather easily agitated Connie of season 5 and beyond.
So as far as I know, this is where her character changed.
So here's the plot. Minh and Kahn are going out to some sort of award ceremony for Kahn and Connie is left with the Hills. Things are cool at first but Bobby starts to worry about how to act around Connie, so he starts acting it's around this time that Connie suddenly starts being a jerk.
Well, it turns out she's becoming a woman. Yeah, and she ends up needing help at the moment that Peggy isn't home. It ends up being a pretty intense episode, considering it shows what dicks Minh and Kahn are. On top of being angry for the first time (that I've seen), Connie also cried for the first time (that I've seen), and both were with good reason. She's been overworked by her parents and now, when she needs them the most, they're off on vacation! You feel sorry for Bobby, too, considering he hasn't hit puberty yet, so suddenly it's like there's this whole world between him and Connie.
Looking back, this could be considered the beginning of the end for Bobby and Connie's relationship, since she's becoming a woman and he'll always be a kid. Of course, it's still a damn good episode, as all of KOTH of seasons 1-5 was.