Funny Celebrity Joke

Anna boyfriend walked into the annas house and the anna said to her mom, "Mom, me and my boyfriend are going up to my room" and the mom says, "Ok honey, you kids have fun." When they are up their the mom hears: "Baby baby baby oh!" The mom walks to the door and ask, "What the hell is going on?" The anna says, "Mom were just having sex." and the mom says, "Oh thank god I thought you guys were listening to Justin Bieber."