Katy Perry, John Mayer Dress Up Early for Halloween

Katy Perry and John Mayer, who are rumored to be dating, have celebrated Halloween together early this year.

Just days after being spotted together in New York City, the singers attended a star-studded costume party at Los Angeles' Magic Castle on Friday, according to ABC News.

Perry, who turns 28 on Thursday, donned a crimson coat over a white dress, fake fangs, and red contact lenses in a vampire costume. Alternately, Mayer, who celebrated his 35th birthday last week, wore a prosthetic nose and chin in addition to a bloodied shirt, completing his zombie hunter outift.

The event also saw "Twilight" star Kristen Stewart, "Raising Hope" star Shannon Woodward, Perry's brother David Hudson, her stylist Johnny Wujek, and actor Matt Dallas.

On Twitter, Perry used her birthday to promote meditation.

"Transcendental meditation changed my life," wrote the "Part of Me" singer. "For my birthday I would love to pay it forward. In lieu of gifts, donate," and provided a link to the David Lynch Foundation.

She later responded to R&B singer Frank Ocean's birthday wishes on Twitter, writing, "Thanks darling.'"

Perry and Mayer posed for several pictures during Friday's bash, including one where the pair appeared to be leaning in for a kiss.

Despite long-standing rumors of their romance, the couple has never been photographed holding hands or displaying any closer affection toward one another.

While in NYC earlier last week, the pair avoided cameras while dressed up for a quiet dinner.

Rumors of their relationship began earlier this summer, but some fans are concerned that Perry will end up heartbroken. Mayer has been linked to several women including Jennifer Aniston, Taylor Swift, Jessica Simpson, and others in the past.

"Katy's friends and family haven't taken to John at all, in fact they are worried that she is headed for heart break," said a source close to Perry, according to RadarOnline.com.

"She's been telling everybody who cares to listen how great John is and it's clear that she is totally in love with him," the insider added.