Played: Dr. Drew Baird, starting in season 3's "Generalissimo," and Abner in season 6's "Live from Studio 6H"

The "Mad Men" star had already demonstrated a surprisingly deft comic touch with an "SNL" appearance a few months before he turned up on "30 Rock" as Liz's doctor boyfriend. But it was as Drew — so handsome he was the model for Prince Eric in "The Little Mermaid" — that Hamm demonstrated a willingness to do anything for a laugh that seemed the diametric opposite of his cold, controlled performance as Don Draper. Season 3's "The Bubble," in which Liz discovers that Drew is terrible at everything, but gets a pass because of how good-looking he is, is on the short list of best "30 Rock" episodes ever. And all of it revolves around Hamm's willingness to play the fool, whether he's struggling to perform the Heimlich maneuver or throwing a tantrum ("This racquet is a fart!") when Liz beats him at tennis. To cement his position as an inner circle member of the "30 Rock" guest star hall of fame, Hamm popped up in blackface for "Live from Studio 6H"s "Amos and Andy" spoof "Alfie and Abner," spouting offensive dialogue ("I's done stole dis catfish!"), doing goofy dances and abandoning even the slightest pretense of dignity.

- Alan Sepinwall