Wednesday

Caught in the Act!

05/20/2009 at 06:00 AM EDT

• John Mayer, serenading an 18-year-old fan (and her friends) with "Happy Birthday" at Katsuya Hollywood. The rocker was dining at the sushi hot spot, and headed to the bathroom when the ladies noticed him – and started swooning and screaming. So, he approached their table and started singing. After his performance, Mayer gave the birthday girl a kiss on the cheek!

• Mandy Moore, shopping at L.A. vintage store What Comes Around Goes Around with husband Ryan Adams. While Moore scoured the store top to bottom, her musician hubby was searching for a pair of boots. After trying on several pieces, Moore bought a plain white T-shirt and another with the slogan "I'm With the Band."

• Rumer Willis, smooching boyfriend Micah Alberti outside Crustacean Beverly Hills, where she hosted The Bash, a charity benefit for teen patients at Children's Hospital Los Angeles. Once inside the party, the starlet happily mingled with other guests, munched on garlic noodles and, of course, hung near Alberti.

• Jennifer Love Hewitt and boyfriend Jamie Kennedy, hanging out at the Hotel Gansevoort in N.Y.C.'s Meatpacking District with Kennedy's pet Chihuahua. Also at the Gansevoort: Vanessa Hudgens, who checked in with her dad.

•Bill Paxton preparing for his flight at the Dallas-Fort Worth International Airport, where the Big Love star made a good impression in the security line. "He could not have been more of a gentleman," gushed an onlooker, who added that he let her cut in front of him in line. When there weren't enough bins for travelers to put their belongings in before the security screening, the actor went over to another line and returned with "about six bins so the people behind him could have some as well," the onlooker says.

• By ALEXIS CHIU, JENNIFER GARCIA, KRISTEN MASCIA and LESLEY MESSER

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