Hayden Panettiere and Milo Ventimiglia
09/09/2008 AT 06:00 AM EDT
and Milo Ventimiglia
, dining in the living room of West Hollywood's Chateau Marmont at a dinner party for new Web site Talenthouse.com. The Heroes
costars (and real-life couple) stopped into the curtained-off dinner early in the evening – and while they avoided being photographed together, they sure were affectionate. Panettiere sat on her beau's lap, and the two held hands before the meal was served, an onlooker tells us.
And the dinner party was teeming with celebrity couples: Paris Hilton
and Benji Madden
grabbed a table near the open bar, and Hilton sat between her boyfriend and music mogul Russell Simmons
, who kept the heiress laughing all night. While Hilton was game for dinner – feasting on arugula and spinach salad, beef and mashed potatoes – she took one bite of the lemon bar and brownie desserts, and then put them back on the tray. Meanwhile, Hilton's sister Nicky
attended with beau David Katzenberg
, and Sacha Baron Cohen
stopped in later with Isla Fisher.
The pair ate on the garden patio, but later joined the party, sitting on a couch and chatting with friends.
In New York for Mercedes-Benz Fashion Week, Uma Thurman
, hanging backstage at the W Suite before the Diane von Furstenberg
show with fiancé Arpad "Arki" Busson
. The couple stuck close to the bar for a while, sipping mimosas and trying on paper 3D glasses that split the room into prisms. The couple eventually retreated to a corner for some privacy. Also backstage: Jennifer Lopez
, who also sipped a mimosa and, later, got chatty with Rosario Dawson
when the two were asked to stand next to each other to pose for pictures. (See
all the latest sightings from Fashion Week!)
An elegant Keira Knightley
, laughing and chatting with a male friend during a party at the Park Hyatt in Toronto. The actress wore a dark dress and her hair down in loose curls at the party, which also drew out Gerard Butler
, who shared a loud, jovial conversation with a male pal on the smoking patio.
, eating dinner at The Stork in Los Angeles. The starlet dined with a large group – and looked like she was having a blast, an onlooker tells us. Later in the night, new Dancing with the Stars
contestant Lance Bass
arrived at The Stork's club with two friends in tow. Bass grabbed a drink, and settled in for a low-key time with his friends, just chatting and observing the scene in the club.
, shopping with his wife at West Side Kids, a toy store on New York's Upper West Side. The politician looked at Benjamin Franklin and Thomas Jefferson dolls – then headed to brunch at Good Enough to Eat.
By BETSY GLEICK, LESLEY MESSER and JEFFREY SLONIMMonday's Couples Watch >