Britney Spears is back on the market thanks to an understanding Nevada judge who helped the singer undo her quickie Vegas wedding 55 hours after she tied the knot.

Couples need to prove their union meets one of six valid reasons for annulment: unsound mind, physical incapacity, force, fraud, prior existing marriage or underage participants. "Unsound mind" is often a nice way of saying "they were wasted," but not for Spears and longtime friend Jason Allen Alexander.

"Usually people who do this in Vegas are real drunk, but that wasn't the case. She wasn't drunk, not even close," said a source close to the situation.

Spears instead claimed her grounds for being of unsound mind were that she didn't understand what she was getting herself into when she wed Alexander at Las Vegas' Little White Wedding Chapel on the Strip in the early morning hours on Sunday (see [article id="1484029"]"Britney Spears Married In Las Vegas, At Least For A Little While"[/article]).

In her complaint for annulment, filed Monday, Spears said she "lacked understanding of her actions to the extent that she was incapable of agreeing to the marriage," because she and her weekend husband had never seriously discussed the issue. They "did not know each others' likes and dislikes, each others' desires to have or not have children and each others' desires as to state of residency," the complaint read. Once they learned these things about each other, the paperwork claimed, they realized they were incompatible.

They might have realized these things sooner had they been seriously contemplating getting hitched. But the two weren't even seriously dating, according to a source close to the situation, who said Spears had been hooking up with Alexander as well as a number of other people, including one of her dancers, during her festive New Year's holiday weekend.

"She was staying in the Real World suite at the Palms [Casino Hotel] with some dancers and some friends," including Alexander, "and got caught up in the excitement," the source said. "She was just caught up in the moment. It was the funniest thing. During the ceremony, he was dead-on serious about it, and she's just got the biggest smile on her face, like it was just a big joke. Well, who knows what goes on in her mind?"

"It was just crazy, man," Alexander told "Access Hollywood" in an interview at his home Monday morning. "And we were just looking at each other and said, 'Let's do something wild, crazy. Let's go get married, just for the hell of it.' "

In fact, "Britney Spears and a friend took a joke too far by getting married" is exactly how the singer's reps described it.

Spears' attorney filed the complaint for annulment on Monday, with a requisite $122 fee. Within two hours of its filing, Clark County Judge Lisa M. Brown signed off on the paperwork declaring the marriage null and void.

Both Spears and Alexander filed agreements with the court that there would be no community property divided between them, nor any spousal support, Spears' lawyer David Chesnoff said. "She made a mature and responsible decision to back out," Chesnoff said. "They're both pleased with the outcome. It's all done, it's over."

This wasn't the first time Spears had some fun with the idea of getting married. Nearly two years ago she said "I do" to a British television host (see [article id="1453110"]"Britney Says 'I'm Single' And 'I Do' In TV Wedding Farce"[/article]).

For more on Britney Spears, check out the feature [article id="1480286"]"Britney Spears: 'I Don't Want To Be A Tease.' "[/article]

[This story was updated on 01.05.2004 at 6:09 p.m. ET]