Will Ferrell Sings "West Side Story" On Letterman (VIDEO)

04/14/2009 05:12 am ET | Updated May 25, 2011

Will Ferrell stopped by David Letterman's show Friday night to promote Saturday night's simulcast of his Broadway show "You're Welcome America" and ended singing a mashup of "West Side Story."

Ferrell told Letterman, "I've been bitten by the Broadway bug... When the run ends I'm going right in to West Side Story... this would be almost a dress rehearsal for me."

With that, he clucked his tongue, started snapping his fingers and began singing "Maria," complete with some of his own lyrics. WATCH: