Bryan Cranston
Appeared on: "The Mom and Pop Store" (Season 6, Episode 8); four other episodes
Role on "Seinfeld": Tim Whatley, Jerry's dentist
Since "Seinfeld": Cranston starred on Fox's "Malcolm in the Middle" in the early 2000s before landing his seminal role as Walter White on AMC's "Breaking Bad."
James Spader? Really? Every heard of Pretty in Pink, or Less than Zero, etc etc...