25. Keith Hernandez
Best-known episode: "The Boyfriend"
Arguably the greatest sitcom guest role by a professional athlete, Keith Hernandez — a baseball legend who played an indispensable role in helping Jerry's beloved New York Mets win the 1986 World Series — staged an unforgettable bromance with the stand-up comic, only to see the friendship erode after it becomes a bizarre love triangle with Elaine. The moustached Met also provided us with one of the most cockiest bits of dialogue ever by simply declaring, "I'm Keith Hernandez." (And don't even get us started on the Roger McDowell cameo in that spitting incident Zapruder film.) Between Keith's '86 heroics, his role on the best broadcasting team in baseball, and his memorable guest spot on Seinfeld, it's a travesty Hernandez's #17 hasn't been retired at Citi Field yet. DANIEL KREPS