From Heidi Klum as Jessica Rabbit to Katy Perry as Hillary Clinton, these are some of the most outrageous and memorable costumes celebrities have donned throughout the years.
Savannah Guthrie and Matt Lauer
Savannah Guthrie as Kenny Rogers and Matt Lauer as Dolly Parton perform during NBC's "Today" show at Rockefeller Plaza in Manhattan on Tuesday, Oct. 31, 2017.
Heidi Klum was unrecognizable as Michael Jackson from his "Thriller" video during her 18th annual Halloween Party, held at the Magic Hour Rooftop Bar & Lounge on Tuesday, Oct. 31, 2017.
Neil Patrick Harris and family
Neil Patrick Harris, David Burtka and their children, Harper and Gideon, joined the freak show in a creepy carnival-themed Halloween, in a photo from Oct. 30, 2017.
On Thursday, Oct. 26, 2017's episode of NBC's "Superstore," America Ferrera dressed up as late singer Selena.
Brad Falchuk and Gwyneth Paltrow
Gwyneth Paltrow poked fun at her own role in the 1995 film "Seven" while boyfriend Brad Falchuk dressed as Kevin Spacey's character, in a photo she posted to her Instagram account on Sunday, Oct. 29, 2017.
Justin Timberlake and Jessica Biel
After providing voice acting for the movie "Trolls" in 2016, Justin Timberlake, his wife, Jessica Biel, and their son dressed up as the characters Poppy and Branch for Halloween that year.
Bette Midler reprised her role as Winifred Sanderson from "Hocus Pocus" for her Halloween costume in 2016.
Katy Perry and Orlando Bloom
"❤️BILL & HILL 4EVA❤️ ..." Katy Perry captioned this photo of her as Hillary Clinton and Orlando Bloom as Bill Clinton for Halloween 2016.
Beyoncé and Jay-Z
Beyoncé and Jay-Z dressed up as Barbie and Ken for Halloween 2016. Blue Ivy, front, also went as Barbie.
Scott Eastwood, who is Clint Eastwood's son, dressed up as his dad's character from "The Good, the Bad and the Ugly" on Halloween 2016.
One of Kylie Jenner's most iconic Halloween looks was her 2016 costume as Christina Aguilera in her "Dirty" music video.
Taylor Swift dressed as Olaf from "Frozen" for Halloween 2015.
Colton Haynes was virtually unrecognizable as Ursula from "The Little Mermaid" in this photo posted to his Instagram before Halloween 2015.
Neil Patrick Harris and David Burtka
Neil Patrick Harris, top right, David Burtka and their twins, Harper and Gideon, dressed as Obi-Wan Kenobi, Han Solo, Princess Leia and Luke Skywalker from "Star Wars" on Halloween 2015.
Gigi Hadid channeled Olivia Newton-John with her Sandy from "Grease" costume on Halloween 2015.
Heidi Klum's Jessica Rabbit costume from Halloween 2015 was quite possibly her most memorable thanks to the prosthetics that seemed to make her look like a living cartoon.
Al Roker and Matt Lauer
The "Today" show anchors Al Roker and Matt Lauer dressed up as "Peanuts" characters, which seemed to cause more shrieks than cheers on Halloween 2015.
Justin Bieber posted a photo to his Instagram account on Halloween 2014, to show off his and his younger brother's Power Ranger costumes.
Colton Haynes shared a photo of his outrageous Fiona (from "Shrek") costume on Instagram during Halloween 2014.
Carmen Electra and Matt Lauer
Former "Baywatch" star Carmen Electra and "Today" anchor Matt Lauer both channeled Pam Anderson's character, C.J. Parker, for Halloween 2013.
Heidi Klum is known to go all out for Halloween; this iconic look (an aged version of herself) was her costume in 2013.
Miley Cyrus' Lil Kim costume at the 1999 MTV Video Music Awards earned tons of feedback on Halloween 2013.
While Miley Cyrus was dressed up in another iconic costume at the MTV Video Music Awards, Perez Hilton dressed up as Miley Cyrus at the 2013 MTV VMAs.
Jenni "JWoww" Farley
Jenni "JWoww" Farley was the Queen of Hearts from "Alice in Wonderland" for Halloween 2013.
Neil Patrick Harris and David Burtka
Neil Patrick Harris and his husband, David Burtka, with their twins Harper and Gideon, dressed up as characters from "Alice in Wonderland" on Halloween 2013.
Miley Cyrus caused some controversy when she dressed up as fellow performer Nicki Minaj for Halloween 2012.
"One Upon a Time" actress Ginnifer Goodwin shared this photo of her dressed up as Rosemary from "Rosemary's Baby" in 2012. She even completed the costume with a demonic baby doll.
NBC's "Today" anchors dressed up as the Kardashian clan for the 2011 Halloween episode. Melissa Francis was Kourtney Kardashian, left, Jenna Wolfe was Khloe Kardashian, Lester Holt was Bruce Jenner, Amy Roebuck was Kim Kardashian and Janice Huff was Kris Jenner.
Fergie dressed up as a contestant from TLC's reality show "Toddlers & Tiaras" for Halloween in 2011.
Regis Philbin and Kelly Ripa
Regis Philbin, dressed up as Mike "The Situation" Sorrentino and Kelly Ripa, dressed up as Nicole "Snooki" Polizzi, from MTV's "Jersey Shore," during the Halloween edition of "Live! With Regis and Kelly" in 2010.
Actress Melissa Rycroft dressed up as Nicole "Snooki" Polizzi for a Halloween charity event in 2010.
During a Halloween party in 2009, Perez Hilton dressed up as Lady Gaga complete with a hair bow, which was her signature look at the time.
For her ninth annual Halloween party, Heidi Klum dressed up as the Hindu Goddess Kali in 2008.
Heidi Klum dressed as Betty Boop for her third annual Halloween Party in 2002.
Arnold Schwarzenegger and Jamie Lee Curtis
Arnold Schwarzenegger and Jamie Lee Curtis dressed up as Dr. Ken and Nurse Barbie for a Halloween charity event on Oct. 27, 2001.
Cher dressed up as ancient Egyptian ruler Cleopatra for Halloween in 1988.