By Breaking Celebrity News Staff

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 Breaking Celebrity News has the pictures.

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.