Halloween 2015: Celebrities get in costume

The "Arrow" star Colton Haynes went all out this year and dressed up as Ursula from "The Little Mermaid" for Halloween.

Nick Jonas

Nick Jonas performs onstage at the Maxim Halloween Party Presented By Karma International on October 24, 2015 in Los Angeles.

Nick Jonas

Nick Jonas attends the Maxim Halloween Party Presented By Karma International on October 24, 2015 in Los Angeles.

Kendra Wilkinson

Kendra Wilkinson attends the annual Halloween party, hosted by Playboy and Hugh Hefner, at the Playboy Mansion on October 24, 2015 in Los Angeles.

Brody Jenner

Brody Jenner deejays during the annual Halloween party, hosted by Playboy and Hugh Hefner, at the Playboy Mansion on October 24, 2015 in Los Angeles.

Mark Salling

Mark Salling (C) attends the annual Halloween party, hosted by Playboy and Hugh Hefner, at the Playboy Mansion on October 24, 2015 in Los Angeles.

Elon Musk, Sean Parker, Talulah Riley

Businessman/inventor Elon Musk, entrepreneur Sean Parker, and actress Talulah Riley attend the annual Halloween party, hosted by Playboy and Hugh Hefner, at the Playboy Mansion on October 24, 2015 in Los Angeles.

Dan Maurio and Diablo Cody

Actor Dan Maurio and screenwriter Diablo Cody attend the annual Halloween Party, hosted by Playboy and Hugh Hefner, at the Playboy Mansion on October 24, 2015 in Los Angeles.

Crystal and Hugh Hefner

Model Crystal Hefner and Hugh Hefner attend the annual Halloween Party, hosted by Playboy and Hugh Hefner, at the Playboy Mansion on October 24, 2015 in Los Angeles.

AJ Michalka, Aly Michalka, Clark Duke

Actress AJ Michalka (L), actress Aly Michalka (C) and actor Clark Duke (second from R) attend the annual Halloween Party, hosted by Playboy and Hugh Hefner, at the Playboy Mansion on October 24, 2015 in Los Angeles.

Lucas Till

Actor Lucas Till attends the annual Halloween Party, hosted by Playboy and Hugh Hefner, at the Playboy Mansion on October 24, 2015 in Los Angeles.

Karrueche Tran

Model Karrueche Tran attends The Official MAXIM Halloween Party produced by Karma International on October 24, 2015 in Beverly Hills.

Mark Ballas and BC Jean

Professional dancer Mark Ballas (R) and BC Jean attend The Official MAXIM Halloween Party produced by Karma International on October 24, 2015 in Beverly Hills.

Aubrey O'Day

Singer Aubrey O'Day attends The Official MAXIM Halloween Party produced by Karma International on October 24, 2015 in Beverly Hills.

Cheryl Burke

Professional dancer Cheryl Burke attends The Official MAXIM Halloween Party produced by Karma International on October 24, 2015 in Beverly Hills.

Chmerkovskiys

Professional dancers Val Chmerkovskiy and Maksim Chmerkovskiy attend The Official MAXIM Halloween Party produced by Karma International on October 24, 2015 in Beverly Hills.

Niecy Nash

Actress Niecy Nash attends The Official MAXIM Halloween Party produced by Karma International on October 24, 2015 in Beverly Hills.

O'Shea Jackson

Actor O'Shea Jackson (C) and guests attend the annual Halloween Party, hosted by Playboy and Hugh Hefner, at the Playboy Mansion on October 24, 2015 in Los Angeles.

Ciara and more

Singer Ciara had a surprise birthday party where guests wore superhero costumes. She posted a photo on Instagram and wrote, "Family Friends and Team Goals..." Among the guests? Beyonce, Kelly Rowland and Serena Williams.

"Grandfathered"

The cast of "Grandfathered" posed for a group Halloween shot. Actress Christina Milian wrote on Instagram, "Who's excited for Halloween?! Uh... We are!"

Kourtney Kardashian

Kourtney Kardashian has the cutest crew, including her three kids, plus sister Kim's daughter North. Kardashian simply captioned the post, "Squad."

Kendra Wilkinson and kids

Kendra Wilkinson Baskett plays with her kids Hank Baskett Baskett IV (R) and Alijah Baskett (L) in Saban's Power Rangers Halloween Costumes on October 26, 2015 in Calabasas.

Lorde

Lorde attends the VEVO Halloween showcase at The Oval Space on October 31, 2013 in London.

Lena Dunham

Ready for it? This is a throwback collage, but Lena Dunham was once (from left, clockwise): a secretary, Medusa and Louis C.K.

Dunham claimed that a starlet pinched her belly and said, "You even did padding and everything!" while Dunham whispered, "That's my real body." You can read her post here.

Iggy Azalea

Iggy Azalea dressed as Cruella de Vil attends the VEVO Halloween showcase at The Oval Space on October 31, 2013 in London.

Taylor Swift

The singer wrote on Instagram: "When you dress as the yellow teletubby for Halloween, but it's before Teletubbies got huge so all the kids at school ask you why you're dressed as a yellow pregnant alien."

Amy Schumer

Here's little Amy Schumer as a witch, we think, but the comedian says we're wrong: "#tbt dressing as myself," wrote the "Trainwreck" star on Instagram.

Lance Bass

Former *NSYNC singer Lance Bass dressed up as a very scary clown.

Bass admitted that he even scared himself: "Alright.... I actually scare myself in this photo! Yikes! And I have to walk around NYC like this!"

Robert Downey Jr.

Robert Downey Jr. put a costume on for a young boy named Daniel who has cystic fibrosis. He invited the boy to the premiere of "Captain America," and wrote on Instagram:

"Mr. Stark here. This is for Daniel (@envy_coatings) who was having a rough day recently. When I'm in the dumps, I've found this little getup to be helpful. P.S. Would you like to come to the LA premiere of Captain America: Civil War as my guest? If so, have your people call my people. All the best."

Miranda Kerr

Miranda Kerr dressed up as Marilyn Monroe for Halloween. The model, as always, looked gorgeous, even if it wasn't the most creative costume.

Hugh Grant

Hugh Grant attends the UNICEF Halloween Ball at One Mayfair on October 29, 2015 in London.

Mariah Carey

Mariah Carey posted this throwback photo of herself on Instagram: The singer once dressed up as a mermaid.

Ashley Madekwe

Lots of people dress up as Mia from "Pulp Fiction" on Halloween, but not all of them get it as right as Ashley Madekwe. The "Revenge" actress even had a fake needle of adrenaline stuck to her chest.

Mario Lopez and Fergie

Mario Lopez posted a throwback photo to when he and Fergie were on "Kids Incorporated."

Kim Kardashian

We think Kim Kardashian is Minnie Mouse in this throwback photo, but we're not so sure. Either way, she was one cute little trick-or-treater!

Ellen DeGeneres

OK -- Karla Kardashian is not a real person, but we laughed at Ellen DeGeneres' costume all the same. DeGeneres paired her costume with a spoof commercial for the newest season of "Keeping Up with the Kardashians."

Holly Robinson Peete

Holly Robinson Peete and Rodney Peete arrive at the Casamigos Tequila Halloween Party on October 30, 2015 in Los Angeles.

Sascha Baron Cohen

Erran Baron Cohen (L) and Sacha Baron Cohen attend the Casamigos Tequila Halloween party at a private residence on October 30, 2015 in Los Angeles.

Russell Simmons

Russell Simmons and guest attend the Casamigos Tequila Halloween party at a private residence on October 30, 2015 in Los Angeles.

Julianne Hough

Julianne Hough attends the Casamigos Tequila Halloween party at a private residence on October 30, 2015 in Los Angeles.

Channing Tatum and Jenna Dewan

Actor Channing Tatum and actress Jenna Dewan attend the Casamigos Tequila Halloween party at a private residence on October 30, 2015 in Los Angeles.

Maria Shriver and Cindy Crawford

Maria Shriver and model Cindy Crawford attend the Casamigos Tequila Halloween party at a private residence on October 30, 2015 in Los Angeles.

Derek Hough

Derek Hough attends the Casamigos Tequila Halloween party at a private residence on October 30, 2015 in Los Angeles.

David Spade

Comedian David Spade attends the Casamigos Tequila Halloween party at a private residence on October 30, 2015 in Los Angeles.

Paris Hilton

Paris Hilton attends Casamigos Tequila Halloween Party on October 30, 2015 in Los Angeles.

Nicole "Snooki" Polizzi

Television personality Nicole "Snooki" Polizzi, Jionni Lavalle and their family dress up as "Star Wars" characters for Halloween on October 31, 2015 at a private residence in New Jersey.

Heidi Klum

Heidi Klum attends Heidi Klum's 16th Annual Halloween Party sponsored by GSN's Hellevator And SVEDKA Vodka At LAVO New York on October 31, 2015 in New York City.

Heidi Klum and Gigi Hadid

Heidi Klum and Gigi Hadid attend Heidi Klum's 16th Annual Halloween Party sponsored by GSN's Hellevator And SVEDKA Vodka At LAVO New York on October 31, 2015 in New York City.

Heidi Klum

Heidi Klum attends Heidi Klum's 16th Annual Halloween Party sponsored by GSN's Hellevator And SVEDKA Vodka At LAVO New York on October 31, 2015 in New York City.

Adam Lambert

Adam Lambert performs onstage at his Ghost Town Halloween Party hosted by Hilton@PLAY at The Beverly Hilton on October 31, 2015 in Beverly Hills, California.

Diane Guerrero

Diane Guerrero attends Heidi Klum's 16th Annual Halloween Party sponsored by GSN's Hellevator And SVEDKA Vodka At LAVO New York on October 31, 2015 in New York City.

Dascha Polanco

Dascha Polanco attends Heidi Klum's 16th Annual Halloween Party sponsored by GSN's Hellevator And SVEDKA Vodka At LAVO New York on October 31, 2015 in New York City.

Jennifer Lopez and Casper Smart

Casper Smart and Jennifer Lopez attend Heidi Klum's 16th Annual Halloween Party sponsored by GSN's Hellevator And SVEDKA Vodka At LAVO New York on October 31, 2015 in New York City.

Shanina Shaik

Shanina Shaik attends Heidi Klum's 16th Annual Halloween Party sponsored by GSN's Hellevator And SVEDKA Vodka At LAVO New York on October 31, 2015 in New York City.

Kelly Bensimon

Kelly Bensimon attends Heidi Klum's 16th Annual Halloween Party sponsored by GSN's Hellevator And SVEDKA Vodka At LAVO New York on October 31, 2015 in New York City.

Jackie Cruz

Jackie Cruz attends Heidi Klum's 16th Annual Halloween Party sponsored by GSN's Hellevator And SVEDKA Vodka At LAVO New York on October 31, 2015 in New York City.

Jay Manuel

Jay Manuel attends Heidi Klum's 16th Annual Halloween Party sponsored by GSN's Hellevator And SVEDKA Vodka At LAVO New York on October 31, 2015 in New York City.

Halloween 2015

Nicole Scherzinger, Casper Smart and Jennifer Lopez attend the Heidi Klum's 16th Annual Halloween Party sponsored by GSN's Hellevator And SVEDKA Vodka At LAVO New York on October 31, 2015 in New York City.

Emily Ratajkowski

Emily Ratajkowski (L) attends the Heidi Klum's 16th Annual Halloween Party sponsored by GSN's Hellevator And SVEDKA Vodka At LAVO New York on October 31, 2015 in New York City.

Jessica Simpson

Jessica Simpson and her husband Eric Johnson dressed up as Christie Brinkley and Clark Griswold from the "National Lampoon's Vacation" series.

Beyonce, Jay Z and Blue Ivy Carter

The Carter family dressed up as characters from the film "Coming to America."

Mariah Carey

Mariah Carey went with a classic witch costume, while her twins dressed up as Batman and Batgirl.

Reese Witherspoon

Reese Witherspoon dressed as a viking for Halloween.

Taylor Swift

Taylor Swift dressed up as Gustav as she took the stage with "Frozen" star Idina Menzel.

Kendall Jenner

Kendall Jenner dressed up as Karl Lagerfeld, the Chanel designer. We're not sure Lagerfeld walks around in a leotard, but it's certainly sexier than his signature suit.

Kylie Jenner

Kylie Jenner wore a sexy warrior costume for Halloween.

Lena Dunham

Lena Dunham called her costume "dead disco."

Allison Williams

Allison Williams even brought a book with her for her "Beauty and the Beast" Belle costume.

Kim Kardashian

Always "Selfish," Kim Kardashian dressed as herself from the 2013 Met Gala for Halloween.

Katy Perry

Mic drop: Katy Perry wore a microphone costume.

Ariana Grande

Ariana Grande traded in her usual cat ears for bunny ears for Halloween.

Nicki Minaj

Nicki Minaj wore a bejeweled costume that seemed to be an ice queen or fairy getup.

Dwayne "The Rock" Johnson

Dwayne "The Rock" Johnson complained on Instagram that his one-size-fits-all Popeye costume was a little too snug.

Miley Cyrus

Miley Cyrus and her friend dressed up as the tooth fairy.

Kourtney Kardashian

Kourtney Kardashian and her little crew dressed up as superheroes again on another day for Halloween festivities.

Kevin Hart

Kevin Hart dressed as his friend Martin Lawrence in the TV series "Martin."

Shakira

Shakira, her husband and two sons dressed as an adorable mouse family.

Lucy Hale

How ap-peeling. "Pretty Little Liars" star Lucy Hale dressed as a peeled banana for Halloween.

Ashley Benson

Ashley Benson of "Pretty Little Liars" donned an orange jumpsuit for Halloween.