But Biel wasn't the only star who got creative at Hudson's bash in the Pacific Palisades. Nicole Richie impressed guests with her spot on Jennifer Lopez costume, complete with the diva's iconic pink sweatsuit, oversized gold aviators, huge hoop earrings and a Louis Vuitton bag.
Sources tell Us Weekly Hudson and a few of her girlfriends "decided to be some sort of playboy bunnies." She and fiance Matt Bellamy "would hug or kiss from time to time, and she was hanging on him with her arm around his neck," added a source. Ryder, 7, and baby Bingham, 3 months, didn't come out for the bash.
Meanwhile, Kim, 31, celebrated the scary holiday on the east coast with her own sexy ensemble. Just two days before filing for divorce from Kris Humphries, the reality star channeled her inner villain by dressing up as Poison Ivy, the hot bad girl made famous by Uma Thurman in 1997's Batman & Robin.
Tell Us: Do you think Jessica Biel was a good Kim Kardashian lookalike?