09/29/2011 at 06:00 AM EDT
and Heidi Klum
had a girls' night out, partying with a group of friends at Beacher's Madhouse inside The Hollywood Roosevelt Hotel
until nearly 2 a.m. The gal pals sat in a back booth and sipped champagne, according to an onlooker. Bullock in particular "had a smile on her face the whole night," and danced to songs including The Clash's "Rock the Casbah" and AC/DC's "You Shook Me All Night Long," the eyewitness said.
had one sweet day – well, evening – at the newly-opened Sprinkles Cupcakes
in N.Y.C. Though she arrived after the shop had closed, the new mom
was given a dozen red velvet cupcakes by the staff as they cleaned up. Perhaps trying to watch her post-baby figure
, Carey also ordered a glass of skim milk to wash the treats down.
and her rumored boyfriend
, Taylor Kinney
of The Vampire Diaries
, spent a wild 48 hours in Atlanta. On their itinerary: a stop by Sister Louisa's Church of the Living Room & Ping Pong Emporium, a dive bar, where Gaga drank Jameson whiskey, participated briefly in the bar's weekly ping pong tournament and posed like a pin-up girl. The next night, the pop star and her crew attended an Atlanta Braves baseball game, then swung by the strip club Clermont Lounge where Gaga – clad in black underwear and black bra – posed with fans until the bar became so crowded her security guards asked her to leave.
had good pals Neil Patrick Harris
and his partner, David Burtka
, on hand at the premiere of his new show, "The Million Dollar Piano," at The Colosseum at Caesars Palace in Las Vegas. Afterward, the group headed to Central Michel Richard restaurant for the afterparty, where they sipped champagne and munched on fried chicken and mashed potatoes, chocolate and fruit.
By JENNIFER BRADLEY, JENNIFER GARCIA and JESSICA WEDEMEYER