Susan Sarandon
Susan Sarandon starred as Jessica Lockhart in season 7 of the series alongside Joey. She played a soap opera star with a flair for the dramatic, maybe even more so than Joey. She appears in Episode 15 "The One with Joey's New Brain."
Paget Brewster
This girl had it all...in terms of boyfriends. She had an impressive multi-episode-arc as the girlfriend of Joey (and Chandler) named Kathy. She was new to the screen back then, but now she's been in Criminal Minds, Community, Law and Order: Special Victims Unit, and Modern Family.