A Fashionable Halloween

Heidi Klum may be the queen of Halloween, but fashion insiders love to get dressed up and play the part of their favorite villains, historical characters, and fellow fashion friends!

In this slideshow: Agyness Deyn, Rosie Huntington-Whiteley, Molly Sims, Gemma Ward, Melissa Haro

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Cleopatra or Petra Nemcova? For Halloween, Petra channeled the beautiful Egyptian queen, elegant hair beads, white flowing gown, and all.

Though you'd hardly recognize her, this is actually Melissa Haro dressed as Harley Quinn from the Batman comics!

Rosie Huntington-Whiteley, Rosie Huntington Whiteley Rosie Huntington-Whiteley went to the Wild West, putting the model moves into her saloon girl costume.

Rosie Huntington-Whiteley went to the Wild West, putting the model moves into her saloon girl costume.

Beverly Johnson showed up at the Roberto Cavalli Halloween party with a gangster mentality. Wouldn't want to be on her bad side!

Sometimes Halloween is all about DIY. And Agyness Deyn proves that the best costumes are always the most innovative. Stripes, bright colors, and best friend Henry Holland as a date sounds perfect!

Some say imitation is the best form of flattery. From the sunglasses to the fitted suit to the gloves, Roberto Cavalli looks every bit the part of Karl Lagerfeld.

Notice how he even went so far as adorning all of his fingers with rings and donning the perfect white wig to look exactly like the Kaiser!

Lydia Hearst unleashed her feminine wiles as a sexy Poison Ivy at a Halloween masquerade she hosted with M.A.C Cosmetics.

It's only appropriate that ethereal beauty Daria Werbowy dress as the ghostly Woman in White. Here she is with a haunting companion at Gemma Ward's Halloween party at Rose Bar.

Fashion's dark prince Gareth Pugh stuck to familiar gothic territory at a Halloween party at Automat Nightclub.

Do blondes really have more fun? Ask Lisa Cant, who went sunshine sweet in this retro-inspired outfit at a party hosted by V Magazine.

Christian Siriano took his cues from Cruella de Vil in this over-the-top puppy frock ensemble.

Zac Posen played crazy clown at Heidi Klum's 3rd Annual Halloween Bash at Capitale in New York City.

Gemma Ward set the gold standard for costume creativity in this Indian goddess getup at V Magazine's "Anything Goes" Halloween party at Rose Bar in the Gramercy Park Hotel.