The audience at the "Late Show with David Letterman" got more than they bargained for yesterday -- and instead of performing just one song, Katy Perry put on a whole 42-minute concert!
Perry performed "Teenage Dream" and "California Gurls," plus older hits "Hot n Cold," "I Kissed a Girl" and "Thinking of You" and other songs from her new album.
CBS put the whole gig online -- check it out above!
