This is one of my favourite episodes in the entire series. It begins funny, like any other episode, until we see the "hot french girl" at the party, who is no one but Topanga. Then, the episode becomes one of the saddest, when they decide to break up and stay friends. What makes it so sad is that, just after leaving, in opposite ways, both realize that what they did could be a mistake, and both returns... but missed each other. The image of Cory, sitting alone, is heartbreaking, and the final scene, with the song "All I know" (one of my favourite nostalgic-songs since then) is so beautiful and well done that makes me cry. That scene reveals exactly what Topanga and Cory are, their story... and, in the end, when they look at each other, we know that what they did is a mistake, and that they know too... but it's done.
Heartbreaking, but, in my opinion, necessary to show them what they need and what they want.