Taylor & Katy's Duet, Christina on Motherhood & Max, & Nude Music Stars Hear Katy Perry sing "Hot N Cold" with Taylor Swift, listen to Christina Aguilera explain why she feels sexier as a mom, and check out Ricky Martin, Britney Spears, and more musicians who stripped down in videos, all on the latest PopSugar Rush! Be sure to follow us on Twitter and become a fan on Facebook for all the latest celebrity gossip!