PHOTO: Katy Perry as a vampire and John Mayer as a zombie hunter at her Halloween Birthday party

John Mayer and Katy Perry are back on, it looks like, or at least they’re back on to posing together for publicity.

Friday night, while Adele was giving birth, 27-year-old Katy Perry celebrated her own birth a little early (her real B-Day is Thursday) with a Halloween-themed birthday bash. It might have been a shared birthday kind of thing, because John turned 35 last week.

Katy was a vampire, complete with creepy red contact lenses, which go well with her jet black hair. John was a dirty zombie hunter, and apparently a prosthetic nose and chin is required for this look.

The pair partied at The Magic Castle in L.A. with a bunch of friends including a Rob-Patless Kristen Stewart.

The other friends, in case you were wondering, were:

Katy‘s brother David Hudson, stylist Johnny Wujek andboyfriend Ricky, jewelry designer BFF Markus Molinari, Raising Hope star Shannon Woodward, DJ Mia Moretti, entrepeneur John Terzian, musician Blue Hamilton, actor Matt Dallas, producer David Ranes, musician Ferras, singer Sarah Hudson, and radio personality Karli Henriquez.

PHOTO via Mark Hunter / The Cobra Snake