Season 3: Episode 54: The One With The Flashback
The gang has a flashback to three years ago (one year before the pilot was supposed to have happened) where we see how everyone's lives were beginning to come together. Phoebe is moving out of Monica's apartment because Monica's too anal retentive. Chandler is searching for a new roommate, who ends up being Joey. Joey soon hits on Monica. Monica bumps into Rachel, whom Chandler has just tried to pick up, at their favorite bar--which we learn is about to become a coffee shop--and Rachel speaks of her recent engagement. And Ross learns that Carol is really a lesbian. Ross is devastated, and Phoebe tries to help. The two end up in a passionate kiss, but the moment is broken when the other friends show up.