Katy Perry and Russell Brand
National Photo Group
05/11/2010 AT 06:00 AM EDT
threw a party to debut her new single "California Gurls" – and the singer made sure she had her favorite treat
with her: red velvet cake. Also there? Her fiancé Russell Brand
and close pals who all fêted the new tune – and a friend's birthday – at Trousdale Lounge in L.A. Nearby, real-life (and virtual) lovebirds Avril Lavigne
and Brody Jenner
, who hung out with the Hills
's star's mom, Linda.
spent Mother's Day shopping at The Grove in West Hollywood with his mom, Pattie
. The two also lunched at the Cheesecake Factory, where the pop star arrived holding a skateboard. He ordered a strawberry lemonade and a milkshake and was also "taking tons of photos with his fans," an onlooker says, adding, "He looked a bit flirtatious with some of the ladies, too."
In New York, Channing Tatum
took shots with his friends at Fanelli's Café in SoHo. Sitting near the window with two guys and a girl, the actor laughed the night away, deep in conversation with his pals at the low-key pub. The next day, Tatum was spotted shopping at Rag & Bone in the West Village.
After a Vegas trip, Audrina Patridge continued
her 25th birthday celebration with boyfriend Ryan Cabrera
at just-opened L.A. nightspot
Las Palmas. The Hills
star, who was joined by close friends, sipped tequila and enjoyed a serenade by Cabrera, who played three songs including an acoustic version of Justin Bieber's "Baby."
, signing the dressing room wall after buying a vintage red scarf, a necklace and scented oil at Sofia, a boutique in Chicago's Gold Coast neighborhood.
By PAUL CHI and JENNIFER GARCIACouples Watch: Fergie & Josh Party After-Hours in London >