Katy Perry Celebrates Birthday in Costume Party With John Mayer

Katy Perry threw an early birthday party on Friday, October 19 in Los Angeles. The West Coast pop singer, who will turn 28 on October 25, was joined by her rocker boyfriend, John Mayer, as she hosted a star-studded costume party at the famed Magic Castle.

Katy dressed up as a sexy blood sucker in a white lace sheer dress. She finished off her vampiric look with fake fangs, a necklace with a giant cross, red-tinted nail polish, and a crown. Her beau wore a bullet belt and rocked a prosthetic nose and chin as the undead hunter.

The guests included Kristen Stewart and Neil Patrick Harris. The "Twilight Saga" actress attended the bash with Robert Pattinson's friend Marcus Foster, while the "How I Met Your Mother" actor was accompanied by his partner David Burtka.

K-Stew opted for a casual number, while Neil dressed up as a vampire. "Thank you @KatyPerry for having @DavidBurtka and me at your frightfully fun B'day Bash at the @MagicCastle last night," the Barney depicter tweeted along with a picture from the party.

Earlier this month, John celebrated his 35th birthday with Katy in a more low-key outing. The "Your Body Is a Wonderland" hitmaker took his girlfriend, his family and some of his close friends to the Freemans restaurant on Manhattan's Lower East Side for a dinner.