Austin Butler, Kaia Gerber and Jenna Dewan were among the other stars at Friday's event.
Hollywood is getting into the Halloween spirit. On Friday, Casamigos threw its annual Halloween party, and A-list stars showed up in some unforgettable costumes to celebrate the holiday.
Megan Fox and Machine Gun Kelly looked to Kill Bill for inspiration, and an eyewitness tells ET that the pair "looked very much together" after a tumultuous period in their relationship.
"They spent most of the night by each other's sides and held hands," the eyewitness says. "They danced a little bit and seemed to be enjoying themselves."
Elsewhere, stars including Jessica Alba and Paris Hilton dressed up as Britney Spears, while Rachel Lindsay channeled Rihanna for her costume.
Meanwhile, it was a family affair for Kaia Gerber, who attended the bash with her beau, Austin Butler, and posed alongside her parents, Rande Gerber and Cindy Crawford, and brother, Presley Gerber, amid the party.
Keep reading to see all the A-list stars dressed for the Halloween party.
Chord Overstreet and Glen Powell as Ricky Bobby and Cal Naughton Jr. from Talladega Nights: The Ballad of Ricky Bobby
Jenna Dewan and Steve Kazee as Kim and Edward Scissorhands from Edward Scissorhands
Justin Bieber as a snorkeler
Kaia Gerber and Austin Butler as Edie Sedgwick and Andy Warhol
Kira Hagaman, Jessica Alba and Kelly Sawyer Patricof as Britney Spears
Megan Fox and Machine Gun Kelly as Gogo Yubari and The Bride from Kill Bill
Paris Hilton as "Toxic"-era Britney Spears and Carter Reum as a pilot
Rachel Lindsay as Rihanna
Rande Gerber and Cindy Crawford as Danny Zuko and Sandy Olsson from Grease
Sarah Hyland and Wells Adams as Virginia Venit and Happy Gilmore from Happy Gilmore
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