Helen Hunt
Helen Hunt, lest we not remember, appeared for a short time in Friends. She played Jamie Buchman in a scene at Central Perk, but her roots with the cast go deeper than that. Lisa Kudrow had her own role on Hunt's show as the ditzy waitress Ursula. Sound familiar?
Ben Stiller
In season 3, Ben Stiller appeared on the show as Tommy, a date for Rachel who also had severe anger management issues. He had no idea that his future wife, Christine Taylor, had been appearing on the show that same season. Talk about kismet!