Caught in the Act

Double Date? Ashlee & Vincent Party with Liam & Miley in L.A.

11/18/2011 at 06:00 AM EST

Ashlee Simpson made it a cozy date night with beau Vincent Piazza at a Google and T-Mobile bash inside L.A.'s Mr. Brainwash Studios. And they weren't the only couple sticking together: Miley Cyrus and on-again boyfriend Liam Hemsworth showed off their moves on the dance floor as Maroon 5 serenaded the starry crowd (guests included everyone from Cory Monteith to Paris Hilton to Chris Brown – with hits like "This Love." As for Simpson and her man, a partygoer tells us they were huddled together in a VIP section where they "hugged up and [acted] very sweet with each other." – Jessica Herndon

NEXT: Zac Efron & Rumer Willis Hit the Club Together