James Spader is Jason Hanky in The Apology (Season 9 Episode 9).

Jarion Monroe is Man in Elevator in The Statue (Season 2 Episode 5).

Jarrad Paul is Darin in The Voice (Season 9 - Episode 2).

Jason Alexander is George Costanza in all Seinfeld episodes except The Pen (Season 3 Episode 3).

Jason Beck is Bouncer in The Bizarro Jerry (Season 8 Episode 3).

Jason Manary is Joey in The Raincoats (Season 5 Episodes 18-19).

Jason Wingreen is Man #2 in The Opera (Season 4 Episode 9).

Jay Brooks is Sid in The Alternate Side (Season 3 Episode 11).

Jay Leno is Himself in The Shower Head (Season 7 - Episode 15).

Jed Mills is Joel in The Non-Fat Yogurt (Season 5 Episode 7).

Jed Rhein is Steven Koren in The Van Buren Boys (Season 8 Episode 14).

Jeff Coopwood is Security Guard in The Fusilli Jerry (Season 6 - Episode 21).

Jeff Hatz is Gene in The Comeback (Season 8 Episode 13).

Jeff Lester is Raymond in The Note (Season 3 Episode 1).

Jeff Yagher is the John Germaine in The Rye (Season 7 Episode 11).

Jeremiah Birkett is Jean-Paul (or Jean-Paul Jean-Paul), the runner from Trinidad and Tobago in The Hot Tub (Season 7 Episode 5).

Jeremy Piven is Michael Barth in The Pilot (Season 4 Episodes 23-24).

Jeremy Roberts is Chaffeur in The Limo (Season 3 Episode 18).

Jerry Dixon is Customer in The Strike (Season 9 Episode 10).

Jerry Hauck is Tim Fields in The Old Man (Season 4 Episode 18).

Jerry Levine is the stationery store guy in The Big Salad (Season 6 - Episode 2).

Jerry Maren is Dad in The Yada Yada (Season 8 - Episode 19).

Jerry Seinfeld is Jerry Seinfeld in all 172 Seinfeld episodes.

Jerry Sroka is Todd in The Lip Reader (Season 5 - Episode 6).

Jerry Stiller is Frank Costanza, George's father in 27 episodes. His first appearance was in The Handicap Spot (Season 4 Episode 22).

Jesee D. Goins is Cop in The Hamptons (Season 5 Episode 21).

Jesee White is Ralph in The Cadillac (Season 7 Episode 14).