Katy Perry's Birthday / Halloween Party

Well, the spooky holiday coincides with Katy's birthday (she turned 24 on October 25); so the singer threw a massive Halloween/birthday bash at Siren Studios in Los Angeles Tuesday night, reports E! Online.

Setting the tone for the event, so-gay Katy arrived at the festivities in a hearse.

More than 200 costumed guests—including Josh Groban and Cisco Adler—packed into the Malibu Rum-sponsored event to creep each other out with their costumes.

Aside from guzzling rum concoctions, partygoers bobbed for body parts and made merry in a coffin photo booth and an execution chamber.

Guests were asked to dress as their favorite dead celebrity. Adorned with a bushy mustache, Katy resurrected deceased Queen frontman Freddie Mercury.

Katy Perry

Katy Perry: I'm No Mariah Carey

"I Kissed a Girl Singer" has said she has no ambitions for MiMi's screen career.

"I would have to have ample amount of time to devote myself to specific movies in order to be any good. It's the perfectionist in me!" the 24-year-old tells the January issue of Saturday Night magazine.

A humble sentiment, until Perry hints at who she thinks hasn't shown such judgment in their own big-screen career.

"Just because I've had success in one area of the entertainment industry does not mean I can go out and make Glitter," said Perry.

Glitter was Mariah Carey's notorious 2001 stab at movie stardom, after over a decade of dominating the record industry. The critically panned film cost $20 million to make and spent two years in development limbo before debuting in September '01 to a paltry $2.41 million opening weekend (grossing a total of under $5 million).

Seven years later the film is mostly cited in discussions of disastrous cross-over attempts, although 38-year-old Carey has had critically acclaimed turns in flicks like Wisegirls and Tennessee.

"Hot N' Cold" singer Perry will instead focus on her next album. She says she wants to work with "Calvin Harris because he created disco, and Ben Folds because he says whatever the f*ck he wants."

Katy Perry in Bikini

Katy Perry - Bikini

Katy Perry