Just because they're grown-ups (well, sort of) doesn't mean Hollywood's biggest stars can't let their inner-kid out at Halloween.

In costumes ranging from elaborate, professionally-made ensembles to outfits pulled together out of their closets, stars hit up countless Halloween parties, and RadarOnline.com has the pictures.

PHOTOS: Kim Kardashian And Other Celebs Dress Up For Halloween

Kim Kardashian was a super-sexy Poison Ivy at the Midori Green party she hosted in New York. Her reality star friend, publicist Jonathan Cheban escorted Kim as Batman's sidekick Robin.

We spotted Brit socialite Petra Ecclestone all decked out in L.A. as Jessica Rabbit. Cameron Diaz stuck a few dollar bills around her waist and attended a friend's bash as a stripper.

Bette Midler squeezed into a corset to host her annual New York Restoration Project fundraiser in Manhattan.  Her pal Stevie Wonder was there as a skeleton and Alan Cumming was a mouse.

Jennifer Aniston and Justin Theroux have packed up, boarded their private jet and departed the Hawaiian island of Kauai after a romantic two week vacation.

The lovebirds had been staying in a rented estate not far from the lavish homes owned by Jen's friend Ben Stiller, plus Better Midler, Pierce Brosnan and Will Smith.

PHOTOS: Jen Aniston And Justin Theroux Board Their private Jet, Leaving Kauai

The two met on the set of Wanderlust, and have been inseparable for the last several months. As RadarOnline.com previously reported, they are already looking for a house to share in Hollywood.

Their movie opens October 7 and they may just walk the red carpet together.

Jennifer Aniston – Horrible Bosses, Terrific Outfit

PHOTOS: Jen Dazzles At London Premiere

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