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

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

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

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.

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.

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.

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.

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.

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

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.

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

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

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

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

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.

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.

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

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

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

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."

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.

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

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

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

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

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!

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

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

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

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

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

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

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

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 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 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 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 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 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 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.

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 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 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 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 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.

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

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

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

Reese Witherspoon dressed as a viking for Halloween.

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

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 wore a sexy warrior costume for Halloween.

Lena Dunham called her costume "dead disco."

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

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

Mic drop: Katy Perry wore a microphone costume.

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

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

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

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

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

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

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

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

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