'The Twilight Saga: New Moon' stars attend a huge fan party in MOh Sugar!

Both Rob Pattinson and Kristen Stewart snuck away on a private date in NYC, while the rest of the cast partied away.

Us magazine reports: Among the small group joining the couple at Avenue was rocker Joan Jett (who Stewart portrays in the film The Runaways). Pattinson — who is also a musician — was particularly fond of Avenue’s rock-heavy playlist. “Robert kind of sang along to the words in the songs he knew,” including “Common People” by Pulp, an observer tells Us.

Adds another eyewitness of Pattinson and Stewart: “They sat very close to each other [and] looked very happy together. They chatted together the entire time.” Their drinks of choice? Amstel Light for him, Belvedere Vodka for her.  When the pair left around 3am, “they were holding hands,” an eyewitness says.

Too cute!

In related news: The Twilight sequel “New Moon” has already set box office history, breaking all records with an estimated $26.3 million from just the midnight showings of the movie.