Bob Odenkirk
Appeared on: "The Abstinence" (Season 8, Episode 9)
Role on "Seinfeld": Ben, Elaine's doctor boyfriend who isn't quite a doctor
Since "Seinfeld": Odenkirk was already starring on "Mr. Show with Bob and David" at the time of this appearance. He went on to star as Saul Goodman in AMC's "Breaking Bad" and "Better Call Saul."
James Spader? Really? Every heard of Pretty in Pink, or Less than Zero, etc etc...