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

SIBLING REVELRY

No, Paris Hilton – in sexy cavewoman mode – isn't being arrested for overexposure. That's her sister Nicky (left) masquerading as a cop as the costumed hotel heiresses head out to a Halloween party in Los Angeles on Friday.