The two arrived together and "kept grabbing each other's hands and Diplo kept pulling Katy in," the observer recalls. When they weren't touchy-feely, the two let loose on the dance floor and chatted with pals like Girls' actress Allison Williams.
DJ Sam Ronson, who was spinning at the star-studded bash, played Perry's smash hit, "Dark Horse," specifically for the pair — and they danced along!
Perry, 29, and the L.A.-based music producer first started seeing each other in April, two months after the singer split — seemingly for good — from her on-and-off-again boyfriend John Mayer. The once-divorced songstress told Rolling Stone earlier this month that she prefers to date fun guys.
"I'm interested in colorful personalities," Perry explained. "Look, I can't be perfect. I don't know. I think you love who you love. You learn over time. I mean, each one has been different. I tweeted the other day that I'm just looking for the prince that fits my glass Jordans slipper."
The couple were joined at Meyers' bash by a slew of celebrity guests including Amy Poehler, Jon Hamm, Claire Danes, and others. "Almost everyone from the Emmys came to Seth's afterparty," the source says. Attendees noshed on dishes like roasted Brussels sprouts, lobster rolls, crostini with burrata and apricot, and (yum!) Nutella banana paninis for dessert.
"The party was so much fun," the eyewitness says. "It kept going until 3 in the morning," even after the bar stopped serving drinks at 2 A.M. "Guests still kept dancing and partying."