The couple spent a night out in Hollywood on Nov. 10 to celebrate the birthdays of HelloGiggles blogger Sophia Rossi and "New Girl" co-creator Liz Meriwether. According to an Us Weekly inside source, Perry and Mayer looked "so affectionate" together.
"John had his hand on Katy's back a lot, and they were kissing and holding hands," the source says. Apparently the couple looked like they were "full-on dating."
Also in attendance were Jon Hamm, Nicole Richie, Mindy Kaling and "New Girl" star/Hello Giggles co-founder Zooey Deschanel. And yes, before you ask, she and Perry were "joking about how they look alike."