Flashback: The best celebrity Halloween costumes of 2015

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'Grease' was the word for Gigi Hadid, one of the many star guests at Jessica Rabbit's – we mean Heidi Klum's! – star-studded annual party sponsored by SVEDKA vodka at Lavo in New York City.
Photo: Getty Images

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Me and Mrs. Bones! Casper Smart and Jennifer Lopez hit the black carpet at Heidi's party, too.
Photo: Getty Images

3/49

Emily Ratajkowski, as Marge Simpson, looked like she jetted in from Springfield for the GSN’s Hellevator sponsored soirée.
Photo: Getty Images

4/49

Nick Cannon and ex Mariah Carey got festivewith their kids at the singer's Halloween bash at her Airbnb Beverly Hills estate.
Photo: Getty Images

5/49

Meanwhile, pop star Ashanti had the blues as an adorable Smurfette.
Photo: Getty Images

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Foxy singer Nicole Scherzinger also stepped out for Heidi's big bash.
Photo: Getty Images

7/49

King Puffy! The host with the most, Sean 'Diddy' Combs hosted a ball with CÎROC apple infused vodka at Marquee in NYC.
Photo: Getty Images

8/49

On the opposite coast, supermodel Alessandra Ambrosio got devilish as she hosted her 'Heaven and Hell' Halloween party presented by VOCO at 1OAK in West Hollywood.
Photo: Getty Images

9/49

Romy & Michelle's Halloween reunion? Jessica Alba and her friend Kelly Sawyer channeled the movie's hilarious characters.
Photo: Instagram/@jessicaalba

10/49

Gwen Stefani brought fright night to the farm.
Photo: Instagram/@gwenstefani

11/49

President Obama met the Pope's mini-me at the White House as kids trick-or-treated on the South Lawn of the White House.
Photo: Getty Images

12/49

The Casamigos Tequila Halloween party in L.A. was the place to be on Halloween eve. Cindy Crawford and Rande Gerber arrived showing off their biker chic style.
Photo: Getty Images

13/49

The already-adorable couple Channing Tatum and Jenna Dewan-Tatum upped the cute stakes as Cats in the Hat.
Photo: Getty Images

14/49

Julianne Hough infused the night with some 'True Romance'.
Photo: Getty Images

15/49

Josh Duhamel and Fergie made for a fashionable couple as Chanel designer Karl Lagerfeld and his cat Choupette.
Photo: Getty Images

16/49

Paris Hilton was the night's warrior princess.
Photo: Getty Images

17/49

Left Shark and Katy Perry were reunited thanks to Michael Strahan and Kelly Ripa outside the 'Live! with Kelly and Michael' studios in New York City.
Photo: Getty Images

18/49

Kim Kardashian snapped this pic of daughter North and niece Penelope all dressed up as Elsa and Anna from 'Frozen.'
Photo: Instagram/@kimkardashian

19/49

Hilaria Baldwin captured her "cool" kitty cat taking a pre- Halloween stroll.
Photo: Instagram/@hilariabaldwin

20/49

Giacomo Gianniotti traded in his Grey's scrubs for a 'Dumb and Dumber' costume with fellow actor Matt Murray.
Photo: Instagram/@giacomo_gianniotti

21/49

Johnathon Schaech had a fun day at the pumpkin patch with wife Julie Solomon and their son Camden dressed as a pair of pumpkins in L.A.
Photo: juliesolomon.net

22/49

Ariana Grande dressed in a cow costume during her visit to 'The Ellen DeGeneres Show.'
Photo: Michael Rozman/Warner Bros

23/49

The anchors at 'Good Morning America' were a variety of pop culture characters for their Halloween themed episode.
Photo: ABC

24/49

Justin Bieber paid homage to Will Ferrell in 'Semi-Pro' with his Jackie Moon costume.
Photo: Instagram/@justinbieber

25/49

Harrison 'Hot Dog' Ford chatted with Jimmy 'Princess Leia' Kimmel on the 'Jimmy Kimmel Live' show.
Photo: Jimmy Kimmel Live

26/49

Looking for the Great Pumpkin? The 'Today' show cast dresses up as the Peanuts gang.
Photo: Instagram/@todayshow

27/49

As Ellen DeGeneres dressed as lost Kardashian sister Karla, Josh Duhamel joined in as Lloyd Christmas from 'Dumb and Dumber' for the talk show host's special Halloween show
Photo: Michael Rozman/Warner Bros

28/49

Princess Diana's niece Lady Kitty Spencer (left) brought high fashion to Halloween.
Photo: Instagram/@kitty.spencer

29/49

Nick Jonas dressed as the McDonald's Hamburglar and stole hearts and burgers during the Maxim Halloween party.
Photo: Getty Images

30/49

Princess Stephanie of Monaco's daughter Pauline Ducruet appeared to be combining Halloween celebrations with #NationalCatDay.
Photo: Instagram

31/49

Some of the cutest bears around! @hilariabaldwin posted this adorable snap of Carmen and Rafael.
Photo: Instagram

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Leona Lewis and Jared Eng dressed up at Medusa and her snake for her Halloween party.
Photo: Instagram/@jaredeng

33/49

Lindsay Lohan was a seductive cat for her pre Halloween celebration.
Photo: Instagram/@lindsaylohan

34/49

Molly Sims and her 8-month-old daughter Scarlett made the purrfect pair of kitty cats.
Photo: Instagram/@mollysims

35/49

Kelly Ripa channeled Kim Kardashian for 'Live with Kelly and Michael's annual Halloween show.
Photo: Instagram/@kellyandmichael

36/49

Guy Fieri – aka Chrissy Teigen – turned up in the heat in the kitchen on ABC's 'The Fab.'
Photo: ABC

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Tyra Banks (left) appeared as Virgin mogul Sir Richard Branson to join Chrissy on the show.
Photo: ABC

38/49

Miranda Kerr traded in her dark tresses for a blonde wig as she transformed into Marilyn Monroe.
Photo: Instagram/@mirandakerr

39/49

Vanessa Hudgens and her longtime love Austin Butler brought John Travolta and Uma Thurman's 'Pulp Fiction' characters to life.
Photo: Instagram/@vanessahudgens

40/49

Channing Tatum dressed up as a "terrifying" Winnie the Pooh for his daughter Everly's Halloween bash.
Photo: Instagram/@channingtatum

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Robert Downey, Jr. used his Tigger costume to cheer up a young fan who was having a rough day.
Photo: Instagram/@robertdowneyjr

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Former Destiny's Child bandmates Beyoncé (second from left) and Kelly Rowland (far right) posed with friends La La Anthony and Angie Beyince at Ciara's birthday bash.
Photo: Instagram/@kellyrowland

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BFF's Ciara and La La Anthony made a fierce pair of superwomen during the party.
Photo: Instagram/@lala

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A league of extraordinary women! Clockwise from top left: Beyoncé's mother Tina Knowles, Kelly Rowland, Ciara, La La Anthony, Serena Williams, Beyoncé, Angie Beyince and Beyoncé.
Photo: Instagram/@ciara

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Comedian Jeff Dye shared his love of costumes with Beyonce' during Ciara's surprise birthday bash.
Photo: Instagram/@jeffdye

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Kourtney Kardashian was on Halloween duty with her three children Mason, Penelope and Reign and her equally adorable niece North West.
Photo: Instagram/@kourtneykardash