Katy Perry's Halloween Costume: Camel's Hump!

Katy Perry and actress pal Shannon Woodward stay covered up as the humps of a camel at Adam Levine's Halloween party at his home on Saturday night (October 31) in Hollywood Hills, Calif.

The twosome arrived at the event via party bus, which also included Katy's BFF Markus Molinari and singer Ferras (both as Arabian Princes); Adam Lambert as a vampire; Leighton Meester's stylist Logan Horne (as a woopie cushion); Calvin Klein model Jamie Dornan, Miley Cyrus's Last Song co-star and rumored boyfriend Liam Hemsworth and writer Karen McCullah Lutz. Noticeably missing: Katy's boyfriend Russell Brand.

Katy didn't have the best time as a camel this year. She wrote on the Twitter, 'Next year I'm gonna be slutty… it was too hot under those humps. Hope your whore-a-ween was spectacular.'

Aboard the party bus was a stripper pole. Katy wrote, 'Things got crazy! We pulled a Miley on the pole… it was a HIT.'

The bus did make one stop before the party: Gelson's Supermarket! Still in costume as a camel, Katy and Shannon walked right in to pick up a few things. Pics below!

20+ pictures inside of Katy Perry's Halloween fun…