6. The 40-Year-Old Virgin (2005)
http://www.youtube.com/watch?v=L3h8LOGGDLQ In the 2nd Judd Apatow film on the list, we follow Steve Carell's titular virgin as he finagles his way through new friendships and the developing relationship between him and the hot grandma Catherine Keener. At the climactic part of the film, Keener lays in bed, exhausted. Carell's Andy sits up in bed and inexplicably starts singing the song Age of Aquarius (Let the Sunshine In) from the musical Hair, as the cast sings along and dances to the credits. Other notable musical sequences in the film include Jane Lynch's lullaby sung to her by a bad, bad man.