Just when you thought you'd seen it all from Britney Spears, the pop princess, 22, has gotten married -- at a little Vegas chapel, wearing a baseball cap, to a childhood friend, sources close to the singer say. A hotel bellman walked her down the aisle.

But before you make any plans to send wedding gifts, a source close to the pop star insists it was all a joke that went too far, and that Spears is already making plans to annul the marriage.

Says someone close to Spears: "I don't know what's going through her mind."

Spears's husband -- at least for the time being -- is named Jason Allen Alexander, and, like the singer, is from Kentwood, La. The two tied the knot early Saturday morning in Las Vegas at the Little White Wedding Chapel on the Strip, sources tell PEOPLE.

The wedding plan was apparently hatched Friday night while Spears and Alexander were partying at Ghostbar, the hip club in the Palms Casino Hotel. The club's bouncers got word that Spears wanted a limo. One of the hotel's lime-green limos was provided, being driven by a hotel bellman, who shuttled the couple to the Little White Wedding Chapel, a famous quick-hitch place where everybody from Dixie Chick Natalie Maines to Bruce and Demi have tied the knot.

Chapel staff told the couple that they couldn't get married without a license, so the pair was taken by the limo to the Clark County Marriage Bureau office in the downtown Las Vegas courthouse at some point after 12:30 a.m. on Saturday. They applied for and were granted the marriage license, then rode back to the chapel, where they were married.

Spears wore jeans and a baseball cap. Alexander had on a casual shirt. The bellman walked Spears down the aisle. There were no friends or family in attendance.

The whole thing was videotaped by the chapel, and Spears has been showing the world's craziest wedding video to friends.

"I don't even know if she loves him," says a source.

The honeymoon, such as it was, took place back at a luxury suite at the Palms immediately after the wedding. Then, Saturday night, Spears dined with her manager, her brother, Palms owner George Maloof and a couple of friends at a hotel steakhouse.

Little is known about Alexander. A source says that he and Spears were childhood friends who recently hooked up -- then hitched up. They had spent New Year's Eve together at the hotel's Rain nightclub, then retired to the suite.

Spears released her fourth album, "In the Zone," last November. It debuted at No. 1 on the album charts. Her concert tour begins in San Diego on March 2.