George Clooney, Rande Gerber Host Casamigos Halloween Party

The best Halloween party in Hollywood went down Friday night in Bev Hills ... a party that has become a frightening tradition!

George Clooney and Rande Gerber hosted the Casamigos bash at the home of Mike Meldman, a developer and, of course, tequila tycoon.

The theme was psychedelic ... check out the neon and graffiti decorations.

As for the celebs who showed up ... David Arquette, Chuck Liddell, Gerard Butler, Cindy Crawford, Dave Grohl, Jessica Biel, Justin Timberlake, Kaitlynn Carter, Maria Menounos, Larsa Pippen, Laverne Cox, Lisa Rinna, Molly Sims, Jeff Probst, Steve Tisch, Nina Dobrev, Paris Hilton, Patrick Schwarzenegger, Pia Miller, Patrick Whitesell, Ryan Phillippe, and tons more.

Cindy Crawford came dressed in a disco costume and Rande Gerber went as a hippy. Paris Hilton dressed as a fancy-looking bunny with large feather ears and satin lingerie. Lisa Rinna paid homage to J Lo's famed Versace dress with her teal and green costume.

Jessica Biel dressed as 90s JT, with the signature tight-blonde curly hair and large diamond stud earring. And, Justin Timberlake dressed as a microphone.

Nina Dobrev dressed as Billie Eilish -- rocking lime-green roots and black tears running down her face. Kaitlynn Carter dressed in a 70s costume, wearing a silver chain dress and go-go boots. Gerard Butler came dressed in a miss-matched psychedelic outfit and no shirt.

Larsa Pippen dressed as a dark angel with a black mini-dress and black feather wings. Patrick Schwarzenegger went as Austin Powers and his girlfriend, Abby Champion, went as a fembot.