From George Clooney to Julia Roberts: The Best Guest Stars on Friends

It may be all about the core six, but the gang had many famous faces join them along the way

CHARLIE SHEEN

The Two and a Half Men star was in the season 2 episode "The One with the Chicken Pox," in which he played an ex-boyfriend of Phoebe's – a sailor who spends years at a time living in a submarine. When he's above ground for two weeks to spend some time with Phoebe, however, the two come down with the chicken pox – but manage to make his stay romantic regardless.