Jessica Chastain, Kate Hudson, & Jessica Alba Go 50s Chic for Katy Perry's Halloween Party

Jessica Chastain, Kate Hudson, and Jessica Alba hit up Katy Perry‘s Halloween party held at Hollywood Legion on Saturday (October 29) in Hollywood.

The guests dressed in 50s chic for the sock hop themed school dance!

Also in attendance at the event were Jessica‘s beau Gian Luca Passi de Preposulo, Ellen Page with girlfriend Samantha Thomas, designer Jennifer Meyer, Seth MacFarlane, and Josh Gad.

“Cuttin’ a rug with all your cats & kittens. Happy Birthday @katyperry #theleastsquarepersonintheroom,” Jes captioned a photo on her Instagram. The party also acted as a celebration of Katy‘s birthday, which fell on October 25.