"If You Leave Me Now" is a soft rock ballad by Peter Cetera of Chicago. It has been sung by Butters in two episodes; the Season Seven episode, "Casa Bonita", and the Season Eight episode, "AWESOM-O".
In "Casa Bonita", Butters Stotch sings this song while in the bomb shelter Eric Cartman tricked him into staying in because of an apparent catastrophe.
In "AWESOM-O", Butters sings this again while he and Cartman, disguised as the A.W.E.S.O.M.-O 4000, go to bed. However, he is unable to finish the song, as Cartman makes him stop singing.
But if you leave me now, you'll take away the biggest part of me.
Oo-oo-ooooo-oo girl, baby please don't go. Eh,