The One Where Ross Finds Out (Season 2, Episode 7)
The Story: Rachel knows Ross loves her but Ross, who’s still dating Julie (Lauren Tom), doesn’t know that she knows. Rachel leaves a drunken phone message in which she confesses her feelings, and when Ross finds out, at first he’s furious with her. But he can’t stay mad for long.
It took a complete season of Cheers for Sam and Diane to get together for the first time, while Ross and Rachel's "will they or won't they?" lasted a season and a third. Their first kiss was like a pressure cooker releasing all of its steam all at once... And, of course, due to some theatrical twists, they'd have to wait a little longer to make things official. Not only is it a relief, but the episode's build-up is funny; Rachel hopping atop Ross' shoulder, attempting to block him from listening to her soused tape, is top-tier physical comedy. The b-plot, in which Chandler soon regrets hiring Monica as his personal trainer, is quite entertaining.
Link: https://www.imdb.com/title/tt0583481