Does anybody know what is the song that is played in Penny's halloween party? the first one

Haha here's this for a coincidence. so i watch glee, and i bought this song "Smile" (glee cast sang it) and i really loved it. while i was listening to it on my ipod i realized the beginning was naggingly familiar. It finallly dawned on me that it was the one played in Penny's halloween party at first. to make sure i listened to the beginnings of both songs and it worked they matched perfectly. The real version is "smile" by lilly allen :)