See "The Hangover".

The first place I ever saw Zach Galifianakis, the dude who played Alan, was in this charming Fiona Apple video:

http://www.youtube.com/watch?v=krTE0AJkqj4

And just today I found this one:

http://www.funnyordie.com/videos/603799136e/you-bring-me-joy-from-zach-galifianakis