Before Katy Perry danced with a Left Shark and kissed a girl (and liked it), she was a backup vocalist for Christian alternative rock band P.O.D. Perry was known as Katy Hudson (which is her real name) when she provided vocals in 2006 for “Goodbye For Now.”
She joined the band on The Tonight Show around the 3:24 mark in the video below and you can see her around 3:36 in the music video above.