It's one of the few places you're likely to run into Demi Moore, Britney Spears, and Paris Hilton — all on the same night. And you might have cavorted with all three social butterflies at downtown hot spot Butter had you managed to sneak into model Carmen Kass' private 25th birthday party on Sept. 17.

Jamie Kennedy and Paris Hilton arrive at Carmen Kass's birthday party at Butter. P. Diddy, Pharrell (of the music duo The Neptunes) and Jay-Z serenaded Kass over her birthday cake, while Spears fired up cigarettes, despite Manhattan's stringent smoking ban, and Hilton partied nearby.

"I just love the place," says Hilton, a regular. "It's so much fun to hang out there with Britney, who's a real sweetheart. I know the owners, and I go there when I'm in town."

It's easy to see why celebrities major and minor slide into Butter, which has built up a steady star following since it opened last spring. In a city where greenery is at a premium and Mother Nature has largely been eradicated, this bar/lounge resembles a serene indoor tree house, complete with wood-paneled walls, chairs carved out of chunks of timber and a massive photo of a birch forest at the far end of the upstairs dining room.

That might explain why an unassuming Matt Damon, who lives in the neighborhood, is a regular, along with Alan Cumming. Kirsten Dunst has dined with boyfriend Jake Gyllenhaal, Jeff Daniels quietly ate with his pals and basketballer Patrick Ewing stopped by to feast on the strip steak.