Katy Perry
The singer appears with freaky makeup just before the holiday. "Shoutout last night's sad girls club," she wrote on Instagram.
Gigi Hadid
"Look at me I'm Sandra Dee!" The supermodel nails the iconic Grease character with House of CB's cropped 'Roche' top at Heidi Klum's Halloween party.
Kylie Jenner
The reality star appears as a Ninja warrior for Halloween 2015.
Kylie Jenner
The reality star also appears as a "snow princess" the day before the holiday.
Nicki Minaj
The rapper kicks off Halloween weekend at 1 OAK Nightclub at the Mirage Hotel & Casino in Las Vegas.
Snooki
The former Jersey Shore star and her family do Star Wars!
Channing Tatum & Jenna Dewan-Tatum
The married couple have a very different take on The Cat in the Hat at George Clooney's Casamigos Tequila Halloween party!
Nicole Scherzinger
After cheering on the New York Mets, the singer gets spooky for Heidi Klum's Halloween party.
Charlotte McKinney
The model showcases a racy look.
Gwen Stefani
The singer rocks a sexy cowgirl costume on the night before Halloween!
Blake Shelton
The Voice coach goes incognito at George Clooney's Casamigos Tequila Halloween party.
Maria Shriver
"Look at my mother working her Halloween costume! Go M-Dogggg @mariashriver," Patrick Schwarzenegger wrote on Twitter with his mom's costume.
Lauren Conrad
The former The Hills star attends George Clooney's Casamigos Tequila Halloween party.
Julianne Hough
The Dancing With the Stars judge appears as Alabama from True Romance at George Clooney's Casamigos Tequila Halloween party.
Cindy Crawford & Rande Gerber
George Clooney's besties rock the rocker looks.
Molly Sims
Rawr!
Allison Williams
"Ugh Belle I've been telling you to get a damn Kindle. #SubwayStyle #HappyHalloween," she wrote on Instagram.
Paris Hilton & Nicky Hilton
The sisters sport sexy costumes at George Clooney's Casamigos Tequila Halloween party.
Jessica Alba & Cash Warren
The Hollywood couple appears as Romy from Romy & Michele's High School Reunion and Maverick from Top Gun.
David Spade
We've got our first celebrity Pizza Rat sighting!
Peta Murgatroyd & Maksim Chmerkovskiy
The Dancing With the Stars pros and on-again, off-again couple are quite the pair of ghouls.
John C. McGinley
The Scrubs alum is a...Green Lantern?
Kyle Richards & Mauricio Umanski
The Real Housewives of Beverly Hills couple make quite the scary duo.
Lori Loughlin
The Full House star and Full House alum goes all Alfred Hitchcock at George Clooney's Casamigos Tequila Halloween party.