Chris Ivery and Ellen Pompeo
02/09/2009 AT 06:00 AM EST
, throwing hubby Chris Ivery
a 41st birthday bash at ONE Sunset in Los Angeles. Guests – like Grey's Anatomy
costar Eric Dane
and wife Rebecca Gayheart
– feasted on a chef's choice tasting menu, which included Maine sea scallops, chestnut tortelloni and truffle mac 'n' cheese. Then, it was time for dessert and another treat: "They sang "Happy Birthday" and Chris smiled through the whole song," says an onlooker. "He and Ellen were really cute together, she wanted to him to have fun and enjoy his birthday."
Meanwhile, Pompeo's Grey's Anatomy
costar Katherine Heigl
and husband Josh Kelley
, "smiling from ear to ear" during a romantic dinner at Kabuki in Hollywood. The happy duo shared sushi during their late-night dinner and enjoyed each other's company, an onlooker says.
, dancing at her table while girlfriend Samantha Ronson
deejayed at L.A.'s Villa Lounge. Sporting a short green dress, a chatty Lohan frequently whispered into Ronson's ear, smiling and laughing. The two were in great spirits, an onlooker says.
, taking wife Courteney Cox Arquette
shopping at West Hollywood's Live! On Sunset, a new clothing store. The actor was in the day before, and he picked up a coffee table book and shirt. Also in the store recently: Ryan Phillippe
and Abbie Cornish
. "Abbie tried on a bunch of stuff and invited Ryan into the dressing room to help her choose," says an onlooker.
, checking out the tunes spun by DJ Five while partying at TAO Las Vegas with Victoria Prince
. The couple shared some smooches on the dancefloor. "They were slow dancing to the fast music and kissing," a source says. "The deejay even played Britney a few times and they weren't fazed."
By JENNIFER GARCIA and MARK GRAYFriday's Caught in the Act >