No matter that Will Ferrell busted out his Harry Caray impression [1] just a couple months ago, he's back again! This time, he's not a leprechaun, and he's in full Harry mode — complete with a loud tie and wacky hair. He pops up briefly in the audience, then he invites himself to the stage to ask David Letterman [2] about his retirement. Honestly, this just reminds us how much we miss Ferrell on Saturday Night Live [3]! Letterman has a ton of guests lined up [4] for his final shows, so this is really just the tip of the iceberg leading up to May 20.