The singer and her fiancé play dress-up in Vegas. Plus: Jennifer Aniston, Denise Richards, Ben & Jen and more

STRONG MEDICINE

Christina Aguilera and fiancé Jordan Bratman play doctor at the singer's Halloween party at Nobu in the Hard Rock Hotel & Casino in Las Vegas on Saturday. (The pair have yet to tie the knot, but Aguilera's nametag already reads "Nurse B.")