Paris Hilton and boyfriend River Viperi get dressed up for a Halloween house party in Beverly Hills.

Hilary Duff arrives at a Halloween house party in Beverly Hills dressed in a Dia de los Muertos costume.

Hilary Duff and husband Mike Comrie are a spooky pair, arriving in costume for the party.

Julianne Hough and Ryan Seacrest go to the party as Bonnie and Clyde.

Seal arrives at the party with a date.

Emma Roberts dresses as her aunt Julia Roberts in ‘Pretty Woman’ for Halloween.

Derek Hough is a Jedi!

Alessandra Ambrosio is a sexy general, arriving with husband Jamie Mazur.

Rosie Huntington-Whiteley shows some leg in her costume.

Evan Ross and his girlfriend arrive ready to party.