The One with the Rumor (Season 8, Episode 9)

The Storyline: It's the traditional Thanksgiving episode, but with a twist: Their visitor is Will, who attended school with Ross, Rachael, and Monica and, like Monica, used to be overweight. Oh, and he's played by Jennifer Aniston's ex-husband, Brad Pitt.

This was still a contentious remark when it debuted in 2001: Brad Pitt is amusing. He could be one of the strangest and most amusing people on the globe. He'd been hilarious previously, in films ranging from 12 Monkeys to True Romance to Snatch. But films like Burn After Reading, Inglourious Basterds, and Once Upon a Time in Hollywood — when he truly let his freak flag fly — were still in the works, and he was largely portraying serious studs. This is, if nothing else, a preview of what was to come in his one and only on-screen appearance beside Anniston.

Link: https://www.imdb.com/title/tt0583642