Skip to the 45 second mark.
Song: Teenage Dream
Artist: Boyce Avenue (it's a cover, the original is by Katy Perry)
Lyrics to this version: link
A/N: Not my video.
'The Boy is Mine' song Preview from Glee Season 1, Episode 18 title 'Laryngitis'.
Other songs in Laryngitis include 'One', 'Jessie's Girl', 'Lady is a Tramp' and 'Rose's Turn'.