Britney's Latest Single: Herself

When Britney Spears upped and wed hometown friend Jason Allen Alexander, it was on a whim. Then, she came to her senses and filed for an annulment. Total time as a married woman: 55 hours.

"Plaintiff Spears lacked understanding of her actions to the extent that she was incapable of agreeing to the marriage," the annulment petition said.

It took the judge about two hours Monday to act on the "complaint for annulment" filed at 10:12 a.m. in Clark County Family Court. Judge Lisa M. Brown signed the uncontested order, and her decree was filed at 12:24 p.m.

"There is no marriage now," said Spears' attorney, David Chesnoff of Las Vegas. "Jason agreed to this completely. They've made a wise decision. I know they care about each other. They are friends."

The pop superstar married Alexander, who like Spears hails from Kentwood, La., about 5:30 a.m. Saturday at a Las Vegas wedding chapel. She was not intoxicated during the ceremony, according to Chesnoff.

"Absolutely not," he said.

Spears woke up that morning a "little stunned" that she tied the knot, according to a friend who spoke to her several hours afterward. The friend spoke on condition of anonymity.

Alexander said he and Spears hatched the idea to get hitched early Saturday morning.

"We was just chillin' at the room, and we was in Las Vegas, and we were sitting in the room, and we were like, 'Let's go do something. You know, let's go get married,'" Alexander told "Inside Edition" in an interview.

Two eyewitnesses, who were at the chapel for their own elopement and wished to remain anonymous because their parents don't know about it, told "Entertainment Tonight" about what they saw.

"My wife noticed that she was nervous, and I noticed, too," the groom said of Spears. "When I looked at her, her hand was shaking with the paper, and you could see the paper kind of fluttering.

"He didn't seem nervous," the groom said of Alexander. "He seemed a bit blank."

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According to the petition, "Before entering into the marriage the plaintiff and defendant did not know each other's likes and dislikes, each other's desires to have or not have children, and each other's desires as to state of residency. Upon learning of each other's desires, they are so incompatible that there was a want of understanding of each other's actions in entering into this marriage."

The marriage-to-annulment escapade might have been the shortest in the history of Sin City.

"That was fast," said attorney Brian J. Steinberg, who practices family law in Las Vegas. "I'm not even sure they had time to have sex."

Marriage is a legal contract. An annulment acknowledges that there was some inherent problem with the contract or how it was executed, Steinberg said. An annulment dissolves a marriage as if it never happened, while a divorce recognizes that it did occur.

Steinberg said the longer the two waited, the harder it would have been to get an annulment.

"The only reason they are getting it done so quickly is that both parties agree," he said. "I can imagine there are reasons to getting this thing done lickety-split. If you don't, the longer you let this thing sit there more it could turn contested."

Spears' record label, Jive, released a statement saying that Spears and Alexander "took a joke too far." Calls to Spears' representatives were not returned.

Spears and Alexander, a junior at Southeastern Louisiana University in Hammond, La., traveled by limousine to the Little White Wedding Chapel on the Strip after a stop at the Ghostbar, a club in the Palms Casino Hotel.

The chapel staff told the couple they couldn't get married without a license, so they were taken to get a license and driven back to the chapel, where they were married.

The bride wore a baseball cap and torn jeans down the aisle and was escorted by a Palms limousine driver.

Charlotte Richards, the wedding chapel's owner and one of its minister, said the two were sober.

"We do not marry anybody who is inebriated," Richards said. "They have to be fully aware of what they are doing."

Spears snuck out of the Palms hotel early Monday morning.

The singer released her fourth album, "In the Zone," in November. It debuted at the top of the album charts. She begins a concert tour March 2 in San Diego.