(Yup Friends has had some great guest appearances, Charlie Sheen, Brooke Shields, Bruce Willis, Julia Roberts, Jean Claude Van Damn and many more. Be sure and watch "TOW after the Super Bowl," to see lots of celebs)
Jessica Hecht as Susan Bunch
Jane Sibbett as Carol Willick
David Arquette as Ursula's stalker
Hank Azaria as David, a scientist who dates Phoebe (12/94) who later returns in multiple episodes
Catherine Bell as Dianne (1996)
Shelley Berman as Mr. Kaplan, Jr. (1996-97)
Corinne Bohrer as Fruit Basket Girlfriend (5/95)
Dan Castellaneta as the Zoo keeper (01/96)
George Clooney as Dr. Mitchelle (ep. 'one with two parts, The: Part 2 (2/95)')
Elinor Donahue as Monica and Ross' Aunt Lillian (11/94)
Steven Eckholdt as Mark (1997)
Morgan Fairchild as Chandler's mother Nora Bing (01/95)
Jon Favreau as computer millionaire and ultimate fighter Pete.
Lee Garlington as Ronni Rappelano (ep. 'One with the Boobies, The (1995)')
Adam Goldberg as Chandler's new roommate Eddie (2/96)
Carlos Gomez as Julio (ep. '1/16/97)')
Jill Goodacre as herself (1994)
Elliott Gould as Jack Geller
Jennifer Grant (II) as Nina Bookbinder, the woman Chandler had to fire (2/95)
Jennifer Grey as Rachel's best friend Mindy (04/95)
Michael G. Hagerty as Mr. Treeger, building superintendant
Alaina Reed Hall as the nurse at the ER desk (02/95)
Larry Hankin as Mr. Heckles (1994-1995)
Chris Isaak as Rob, the library worker (1/96)
Stan Kirsch as Ethan (ep. 'One With the Ick Factor, The (1995)')
Ron Leibman as Dr. Green (ep. 'One With The Race Car Bed, The (07/11/1996)')
Audra Lindley as Phoebe's grandmother (12/95)
Jon Lovitz as restaurant owner Steve (02/95)
Michael McKean as Mr. Ratstatter, Mocolate maker (11/95)
Elle McPhearson as JANINE LACROIX, Joey's roomate and "hot dancer girl." Season 6
Heather Medway as Ross's dinner date Kristen (02/95)
Sofia Milos as Aurora (Fall 1994)
Wayne Pere as Max (12/94)
Christina Pickles as Judy Geller
Brittney Powell as Jade (10/95)
Leah Remini as pregnant woman whose baby Joey helps deliver (05/95)
Giovanni Ribisi as Condom Boy (11/95)
Giovanni Ribisi as Phoebe's Long Lost Brother (4/96)
Marissa Ribisi as Betsy (10/31/96)
Julia Roberts as Susie, grade school classmate of Chandler's (1/96)
Isabella Rossellini as Herself (ep. 'One With Frank Jr., The (10/96)')
Camille Saviola as Laundromat user (1995)
Claudia Shear as Fake Monica (4/95)
Charlie Sheen as Ryan, the Navy sailor (5/96)
Brooke Shields as Erica Ford (ep. 'one after the superbowl, The (01/96)')
Jane Sibbett as Ross' ex-wife Carol (periodically)
Jonathan Silverman as Dr. Franzblau (5/95)
Cole & Dylan Sprouse, the "Big Daddy" twins who play Ross' son Ben in later eisodes when he is a little bit older.
Fisher Stevens as Roger (1/95)
Marlo Thomas as Rachel's mother Sandra Green
Lea Thompson as Caroline Duffy (11/95)
Lou Thornton as girl who flees when sees Chandler's bracelet (2/96)
Lauren Tom as Julie (09-11/95)
Brenda Vaccaro as Gloria Tribbiani
Jean-Claude Van Damme as Himself (1/96)
Vincent Ventresca as Fun Bobby (12/94, 01/96)
Mitchell Whitfield as Rachel's ex-fiance Barry
Mae Whitman as Girl Scout, Sarah Tuttle
Fred Willard as Dean Lipson, Zoo administrator (01/96)
Max Wright as Terry, Central Perk manager
Noah Wyle as Dr. Rosen (2/95)
Resee Weatherspoon as Rachel's younger sister, Jill.
Steve Zahn as Duncan (10/12/95)
Solei Moon Frye (Sabrina the Teenage Witch and Punky Brewster) who played Katie in "TOW The Girl Who Hits Joey."
Kristen Davis ("Sex and The City") as Joey's love interest in ep 707
Denise Richards ("Wild Things") as Ross and Monica's cousin in TOW Ross' Cousin.
Susan Surrandon as a soap opera star that Joey is replacing.
Jason Alexander as a suicidal toner salesman that Phoebe tries to save.
Winona Ryder as Rachel's soroity sister in TOW Rachel's Big Kiss
Kathleen Turner as Mr. Bing, Chandler's Dad
Gary Oldman, plays a costar of Joey's in a WWII movie, who spits when acting
Sean Penn as Eric, a school teacher and Ursala's Fiance.
Brad Pitt as Will Colbert, high school Friend of Ross' & Monica's, hater of Rachel.
Christina Applegate as Rachel's other sister, Amy Green.
Jeff Goldblum, plays an actor that Joey has to audition for in "TOW The Mugging."
Paul Rudd as Mike, Phoebe's boyfriend.
Fredie Prinze Jr., as Emma's male nanny, Sandy in "TOW The Male Nanny."
Aisha Tyler as Charlie a fellow Professor of Ross' and a love interest of both Joey and Ross.
Dedee Pfeiffer, played Joey's date Mary Ellen in Episode #3 of Season #9 - "The One With the Pediatrician."