We're coming up on the last two weeks of David Letterman's reign as the Late Show host, and things are getting a little nostalgic. Letterman recently asked Will Ferrell to do his famous Harry Caray impersonation on the show a few months ago, and last night, Ferrell showed up in his sportcaster best (because the first time he was dressed like a leprechaun) to do it for Letterman one last time. Ferrell's Caray invites himself on stage during the opening monologue and the two guys just talk about normal stuff, like current events ("Hey! What are we going to do about this wall in Berlin?"). Ferrell is in prime form, grey hair and thick-rimmed glasses askew and all. Watch it above.