Michelle Trachtenberg(01 of54)
Open Image ModalActress Michelle Trachtenberg attends Heidi Klum's annual Halloween party at the Dream Hotel on Monday, Oct. 31, 2011 in New York. (AP Photo/Evan Agostini) (credit:AP)
Paulina Gretzky(02 of54)
Open Image Modal (credit:Paulina Gretzky/Twitter)
Stacy Ferguson(03 of54)
Open Image ModalSinger Stacy "Fergie" Ferguson attends Heidi Klum's annual Halloween party at the Dream Hotel on Monday, Oct. 31, 2011 in New York. (AP Photo/Evan Agostini) (credit:AP)
Heidi Klum(04 of54)
Open Image ModalHeidi Klum, dressed as Cleopatra, attends her Haunted Holiday Party benefiting Superstorm Sandy relief efforts, on Saturday, Dec. 1, 2012 in New York. Klum's original party, scheduled to be held on Halloween, was postponed due to the storm. (Photo by Charles Sykes/Invision/AP) (credit:AP)
Heidi Klum, Seal(05 of54)
Open Image ModalModel and television personality Heidi Klum, left, and husband Seal attend Heidi Klum's annual Halloween party at the Dream Hotel on Monday, Oct. 31, 2011 in New York. (AP Photo/Evan Agostini) (credit:AP)
Kim Kardashian(06 of54)
Open Image Modal Kim Kardashian attends 2nd Annual Midori Green Halloween Party at Avenue on October 27, 2012 in New York City dressed as a mermaid. (credit:Getty Images)
Katy Perry(07 of54)
Open Image ModalKaty Perry as Jane Lane and Shannon Woodward as Daria. (credit:Katy Perry/Twiiter)
Kate Upton(08 of54)
Open Image ModalModel Kate Upton attends Heidi Klum's annual Halloween party at the Dream Hotel on Monday, Oct. 31, 2011 in New York. (AP Photo/Evan Agostini) (credit:AP)
Debra Messing(09 of54)
Open Image Modal"HAPPY HALLOWEEN!! Me and Mariska starting the night!! #boo," the "Smash" star tweeted Wednesday. (credit:Debra Messing/Twitter)
Darren Criss(10 of54)
Open Image ModalDarren Criss is a boy scout and probably a big fan of "Moonrise Kingdom." (credit:PacificCoastNews)
Jenni 'JWoww' Farley, Roger Mathews(11 of54)
Open Image ModalWe never thought we'd say it, but the "Jersey Shore" star and her fiancé positively geeked it out. (credit:PacificCoastNews)
Christina Milian(12 of54)
Open Image ModalNo sleight of hand here. Christina Milian is the Queen of Hearts. (credit:PacificCoastNews)
Stacy Keibler(13 of54)
Open Image ModalGeorge Clooney's girlfriend is "Black Swan." (credit:PacificCoastNews)
Tish Cyrus, Brandi Cyrus(14 of54)
Open Image ModalPop starlet Miley Cyrus' mum and sister Tish Cyrus and Brandi Cyrus are all dressed up for Halloween as they head to the Roosevelt hotel for a party in Hollywood. (credit:PacificCoastNews)
Jeremy Piven(15 of54)
Open Image ModalJeremy Piven as Che Guevara at the Playboy Mansion Halloween Party in Beverly Hills, California on October 27th, 2012. (credit:FameFlynet)
Sacha Baron Cohen(16 of54)
Open Image ModalSacha Baron Cohen donned a bizarre monkey-cow costume. (credit:FameFlynet)
P. Diddy(17 of54)
Open Image ModalP. Diddy rocked out at the Playboy Mansion Halloween Party in Beverly Hills, California on October 27th, 2012. (credit:FameFlynet)
Brandon Davis(18 of54)
Open Image ModalBrandon Davis at the Playboy Mansion Halloween Party in Beverly Hills, California on October 27th, 2012. (credit:FameFlynet)
Liam Payne(19 of54)
Open Image ModalOne Direction singer Liam Payne does his best Batman in London. (credit:Pacific Coast News)
Lucy Hale(20 of54)
Open Image ModalLucy Hale as a unicorn. (credit:Lucy Hale/Twitter)
Shenae Grimes, Chris March(21 of54)
Open Image ModalIn this Image released by Mattel, actress Shenae Grimes, from the series "90210", left, has a fitting of her Monster High Frankie Stein Halloween costume created by "Project Runway" alum Chris March, Wednesday, Oct. 17, 2012, in El Segundo, Calif. Grimes will be attending "Glee" cast member Matthew Morrison's 3rd Annual Halloween Bash, dressed as Frankie Stein, daughter of Frankenstein, from the popular Monster High franchise. This year, the popular Halloween party will be sponsored by Monster High. (AP Photo/Mattel, Rene Macura) (credit:AP)
Heidi Klum(22 of54)
Open Image Modal Heidi Klum gets fitted for her 13th annual Halloween party at finale sponsored by HobNob Wines, Svedka Vodka And Smartwater on September 3, 2012 in New York City. (credit:Getty Images)
Sarah Hyland(23 of54)
Open Image ModalSarah Hyland as Spinelli from "Recess." (credit:Sarah Hyland/Twitter)
Stacy Keibler(24 of54)
Open Image ModalActress/model Stacy Keibler arrives at Hyde Bellagio at the Bellagio to host a Halloween masquerade party on October 27, 2012 in Las Vegas, Nevada. (credit:Getty Images)
Nicole Scherzinger(25 of54)
Open Image ModalNicole Scherzinger as a vampire. (credit:James Curley/Coalition Pictures)
Kim Kardashian(26 of54)
Open Image ModalKim Kardashian as a leopard. (credit:Kim Kardashian/Twitter)
Holly Madison(27 of54)
Open Image ModalHolly Madison as Sleeping Beauty. (credit:Holly Madison/Twitter)
Fergie(28 of54)
Open Image ModalFergie as Lindsay Lohan. (credit:Fergie/Twitter)
Christina Milian(29 of54)
Open Image ModalChristina Milian as Sulley. (credit:Christina Milian/Twitter)
Fergie & Josh Duhamel(30 of54)
Open Image ModalFergie & Josh Duhamel as Angelyne & Dennis Woodruff. (credit:FameFlynet)
Christina Aguilera(31 of54)
Open Image ModalChristina Aguilera as ??? (credit:Pacific Coast News)
Paris Hilton(32 of54)
Open Image ModalParis Hilton as Alice. (credit:X17Online)
Kris Jenner(33 of54)
Open Image ModalKris Jenner as Wonder Woman. (credit:Kris Jenner/Twitter)
Ashley Benson(34 of54)
Open Image ModalAshley Benson as Tweedle Dee (or Dumb). (credit:Ashley Benson/Twitter)
Hugh Hefner(35 of54)
Open Image ModalHugh Hefner as a vampire. (credit:Hugh Hefner/Twitter)
Holly Madison(36 of54)
Open Image ModalHolly Madison as the Cheshire Cat. (credit:Holly Madison/Twitter)
Jessica Alba, Cash Warren, & Honor Warren(37 of54)
Open Image ModalThe Incredibles (credit:Jessica Alba/Twitter)
Lauren Conrad(38 of54)
Open Image Modal (credit:Lauren Conrad/Twitter)
Hilary Duff(39 of54)
Open Image ModalHilary Duff in a Día de los Muertos costume. (credit:Hilary Duff/Twitter)
Kim Kardashian(40 of54)
Open Image ModalKim Kardashian as Kris Jenner. (credit:Kim Kardashian/Twitter)
Fergie(41 of54)
Open Image ModalFergie as a sexy cat. (credit:Fergie/Twitter)
Ryan Seacrest & Julianne Hough(42 of54)
Open Image ModalBonnie & Clyde (credit:Julianne Hough/Instagram)
Julie Bowen(43 of54)
Open Image ModalJulie Bowen as a scary Bo Peep. (credit:Julie Bowen/WhoSay)
Genevieve Jones & Nicky Hilton(44 of54)
Open Image ModalGenevieve Jones & Nicky Hilton as a KISS member and a leopard. (credit:Genevieve Jones/Twitter)
Adam Lambert(45 of54)
Open Image ModalAdam Lambert as a vampire. (credit:Adam Lambert/Twitter)
Chord Overstreet(46 of54)
Open Image Modal (credit:Chortd Overstreet/Twitter)
Heidi Montag & Crystal Harris(47 of54)
Open Image Modal (credit:Heidi Montag /Twitter)
Jesse McCartney(48 of54)
Open Image Modal (credit:Jesse McCartney/Twitter)
Diddy & Holly Robinson Peete(49 of54)
Open Image ModalAs Prince. (credit:Holly Robinson Peete/Twitter)
Bella Thorne(50 of54)
Open Image ModalBella Thorne as a vampire bride. (credit:Bella Thorne/Twitter)
Liam Payne(51 of54)
Open Image ModalLiam Payne as Batman. (credit:Liam Payne/Twitter)
Shanae Grimes(52 of54)
Open Image ModalShanae Grimes as a skeleton. (credit:Josh Beech/Twitter)
Scott Disick(53 of54)
Open Image ModalScott Disick as Patrick Bateman. (credit:Getty Images)
Nicole Richie(54 of54)
Open Image ModalNicole Richie and friends as Wilderness Girls from "Troop Beverly Hill." (credit:Nicole Richie/Twitter)