Flashback - [s3e6]

Fans often cite this as a top-tier episode because it rewards long-term viewers with "Aha!" moments that explain the characters' quirks and deep-seated bonds. It successfully balances the comedy of their younger selves (Ross's hair, Rachel's old nose) with the genuine emotional stakes of their early struggles.

"Friends" The One with the Flashback (TV Episode 1996) - IMDb [S3E6] Flashback

The episode is famous for showing how close the group came to different romantic configurations: Fans often cite this as a top-tier episode