She has a long way to catch up to Elizabeth Taylor, but Britney Spears moved up another notch this weekend with her second marriage this year- this one to Keven Federline.

Los Angeles- Oops, she said “I do” again – and surprised even her mom!

Pop princess Britney Spears pulled a shocker by marrying dancer Kevin Federline in an ultra-cheesy ceremony weeks ahead of schedule.

Even Britney’s mom, Lynne, thought she was going to an engagement party Saturday night.

But the couple tied the knot instead in a five-minute ceremony at a friend’s Studio City home in Los Angeles, with Britney sporting a new brunette hairdo, and later jamming to 1970s rock anthems.

“He was crying, she was crying,” a source told Star magazine. “It was beautiful.”

The surprise wedding means that Spears, 22, is now stepmother to the two children Federline fathered with the actress Shar Jackson, his ex-girlfriend.

Britney looked luscious in a strapless white gown with a tiara and long veil and carried a bouquet of pink and white roses, witnesses said. Federline, 26, wore a custom-designed black tux.

But no sooner had they swapped platinum wedding bands – plain for her, with diamonds for him – then Spears quickly changed into a velour sweatsuit for the supertacky afterparty at a Hollywood nightclub.

She ordered the entire wedding party to ditch their tuxedos and dresses for loungewear outfits, some of which were emblazoned with “Pimp” and “Pimp Daddy.”

It was a less-than-touching moment No.2 on the year for Britney, who married childhood buddy Jason Alexander on a whim Jan.2 in Las Vegas. That union lasted all of three days before it was annulled.

The newest nuptials for Spears were not supposed to take place for at least a month, and friends and close relatives were told to come to Los Angeles for an engagement party.

A clue that something more serious was afoot could have been the appearance of her father, Jamie, who reportedly checked himself into rehab a few weeks ago to deal with addiction to booze and painkillers.

Britney reportedly had told pals she did not want to walk down the aisle until her dad was sober enough to attend.

The crowd of 15 was staying at an L.A. hotel when they were told about the big switcheroo and ordered to get ready for the shindig.

Spears had told pals she wanted a “storybook wedding,” but opted for the tiny gathering at a friend’s home in the decidedly unglamorous Studio City neighborhood. She spent the day at a spa getting pampered for the big day, and apparently having her hair dyed from her trademark blond.

Federline disappeared early in the morning to avoid seeing the bride-to-be before the wedding.

Paparazzi caught on that something momentous was happening when both families converged on the suburban house in the evening and helicopters soon buzzed overhead.

The couple exchanged vows, then guests dined on chicken fingers, crab cakes, ribs and Waldorf salad. The newlyweds danced to Journey’s “Lights.”

Gift bags included jeans, candy and a silver teardrop key ring with an image of the happy couple cuddling.

The whole party moved to a Sunset Strip nightclub, where Spears and Federline canoodled the night away. And in keeping with the evening’s no-frills theme, there was no open bar and guests had to pay for their own booze.

On a bigger money matter, sources close to Spears say she caved in to her mother’s demands and asked Federline to sign a prenuptial agreement.

Spears had infuriated her mom, who is also her manager, when she swore her marriage to Federline would last forever and resisted having her lawyers draw up the deal. Under California law, Federline could have claimed half the pop singer’s vast fortune if marriage No.2 failed and there were no prenup.

The former teen queen insists, however, that it’s until death does she part. She has been spending plenty of quality time with stepdaughter Kori, 2, and Kori’s newborn brother, Kaleb.

And in a recent People magazine interview, she sang the praises of basic housework and getting pregnant. “I love cleaning, I really do. I’m like Suzy Homemaker. I’m starting to learn how to cook,” she chirped.

“I definitely want to have some kids,” she added. “I see myself with four or five.”