Jami Gertz is Jane or Erica in The Stall (Season 5 Episode 12).
Jane A. Johnston is Mrs. Gack, Todd's Mother in The Calzone (Season 7 Episode 19).
Jane Leeves is Marla Penny, the virgin, in four episodes. The first was The Virgin (Season 4 Episode 10).
Janet Zarish is Rental Car Agent in The Alternate Side (Season 3 Episode 11).
Janice Davies is Building B in The Cadillac Part 2 (Season 7 - Episode 14).
Jason Alexander is George Costanza in all Seinfeld episodes except The Pen (Season 3 Episode 3).
Janeane Garofalo is Jeannie Steinman in The Invitations (Season 7 Episode 24) and in The Foundation (Season 8 Episode 1).
Jeff Coopwood is Security Guard in The Fusilli Jerry (Season 6 - Episode 21).
