Daniel Dae Kim
Six years before Daniel Dae Kim broke through as castaway Jin Kwon on ABC's hit Lost, he appeared in the 1998 episode "The Burning" as Student #1.
Megan Mullally
Five years before she became an NBC star in her own right on Will & Grace, Megan Mullally (who was considered for the role of Elaine before Julia Louis-Dreyfus was cast) played George's girlfriend Betsy in the 1993 episode "The Implant."
Mariska Hargitay
Six years before she began kicking ass as Det. Olivia Benson on Law & Order: SVU, Mariska Hargitay (another contender for the role of Elaine) appeared in the 1993 episode "The Pilot," playing Melissa, an actress auditioning for the role of Elaine in Jerry and George's pilot.
Kathy Griffin
Kathy Griffin appeared on Seinfeld twice, first in 1996 and then again in 1998, as Sally Weaver, an old acquaintance of Jerry's.
Molly Shannon
OK, this one is admittedly a bit of a stretch, as Molly Shannon had already been a Saturday Night Live cast member for two years when she played Elaine's hostile new co-worker Sam in the 1997 episode "The Summer of George," but we love the appearance so much we had to include it.
Catherine Keener
Years before she was taking Steve Carrell's virginity in The 40 Year Old Virgin, Catherine Keener popped up as Jerry's jealous artist girlfriend Nina in the 1992 episode "The Letter."
Peter Krause
The Six Feet Under and Parenthood star played white supremacist Tim in the 1992 episode "The Limo."
Jeremy Piven
Before breaking big as Entourage's Ari Gold, Jeremy Piven appeared in the 1993 episode "The Pilot" as Michael Barth, the actor who landed the role of George in Jerry's NBC pilot.
Lauren Graham
Before she was Lorelai Gilmore, Lauren Graham guest-starred in the 1997 episode "The Millennium" as Valerie, Jerry's speed dial-obsessed girlfriend.
Patton Oswalt
In one of his earliest on-screen credits, the stand-up comedian appeared in the 1994 episode "The Couch" as a video store clerk.
Brad Garrett
Months before he got his big break as Robert Barone in CBS' Everybody Loves Raymond, Brad Garrett appeared in the 1996 episode "The Bottle Deposit" as Tony, the psychotic auto mechanic who steals Jerry's car.
Michael Chiklis
Before he landed his starring roles in The Commish and The Shield, Michael Chiklis appeared in the 1991 episode "The Stranded" as Steve Pocatello, George's co-worker throwing a party out on Long Island.
Jane Leeves
A year before she landed the role of Daphne in NBC's Frasier, Jane Leeves appeared in a handful of Seinfeld episodes as the virginal Marla, beginning with 1992's "The Virgin."
Jon Favreau
Years before he entered the MCU as Happy Hogan and began directing hits like The Jungle Book, Jon Favreau appeared in the 1994 episode "The Fire" as Eric the Clown.
Debra Messing
Two years before she became one-half of NBC's hit series Will & Grace, Debra Messing appeared in a pair of Seinfeld episodes as Beth, beginning with 1996's "The Wait Out."
Christine Taylor
The future (and then former) Mrs. Ben Stiller appeared in the 1997 episode "The Van Buren Boys" as Ellen.
Courteney Cox
In March of 1994, Courteney Cox appeared in the episode "The Wife" as Meryl, Jerry's girlfriend who posed as his wife to get a discount at the local dry cleaners. That fall, she would land her own NBC hit with the premiere of Friends.
Teri Hatcher
Before she was Lois Lane or one of the Desperate Housewives, Teri Hatcher appeared in the 1993 episode "The Implant" as Sidra, Jerry's new girlfriend whom he suspects has breast implants. Say it with us now: "They're real and they're spectacular!" She would return for the series finale in 1998.
Drake Bell
Before he was one half of Nickelodeon's Drake & Josh, Drake Bell was Kenny in the 1998 episode "The Frogger."
Marcia Cross
She'd already been stealing scenes on Melrose Place for a couple of years, but a pre-Desperate Housewives Marcia Cross popped up in a 1997 episode entitled "The Slicer" as Dr. Sara Sitarides, Jerry's dermatologist date.
Jennifer Coolidge
Before she was Stifler's mom or learning the art of the bend and snap, Jennifer Coolidge earned her first on-screen credit in the 1993 episode "The Masseuse" as George's new girlfriend Jodi.
Sarah Silverman
The stand-up comedienne appeared in the 1997 episode "The Money" as Emily, Kramer's girlfriend who he has trouble sleeping with in the same bed.
Denise Richards
Before she was either a Bond girl or a Real Housewife, Denise Richards appeared in the 1993 episode "The Shoes" as Molly, the daughter of NBC's president.
Kristin Davis
A year before Sex and the City made her a household name, Kristin Davis appeared in a pair of 1997 episodes as Jenna, Jerry's girlfriend who unwittingly uses her toothbrush after Jerry knocks it in the toilet.