Newly Svelte Britney Spears Surprises Letterman on Show

Brit is back in shape.

A newly slender Britney Spears, who gave birth to her second child in September, surprised David Letterman on Monday night's "Late Show" by popping up behind him as he was sitting at his desk.

"Oh, my god. ... Nice to see you. How are you? Oh, you look wonderful," Letterman told a smiling Spears, who showed up on the CBS show wearing a very short black dress and sporting a blond bob haircut.

"See, I'm in town, and I'm such a huge fan. ... I had to stop by," said Spears, prompting the talk-show host to gush, "Oh, that's very sweet of you."

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Spears then delivered an ego-bruising zinger: "Uh, no, I wasn't talking about you. I was talking about Will Ferrell."

The 24-year-old singer strode off the set when Letterman directed her backstage to meet Ferrell, his guest on the show.

Spears married rapper Kevin Federline, 28, in 2004. They have a 1-year-old son, Sean Preston, and an infant son, who was born Sept. 12. The couple have not confirmed the infant's name, which is reportedly Jayden James.

Meanwhile, a judge in Los Angles has thrown out Spears' lawsuit against Us Weekly, ruling the pop star cannot be defamed by published rumors that she and Federline had made a sex tape and were worried about its release.

Superior Court Judge Lisa Hart Cole said Spears has "put her modern sexuality squarely, and profitably, before the public eye" and it would be unlikely for the magazine article to be found defamatory.

The judge's decision to dismiss the $10 million lawsuit filed last year did not address whether the October 2005 story was true or false.

"The issue is whether it is defamatory to state that a husband and wife taped themselves engaging in consensual sex," Cole wrote in the decision issued last week. "The backdrop against which this issue must be addressed is that the plaintiff has publicly portrayed herself in a sexual way in her performances, in published photographs and in a reality show."

Spears' lawyer, Martin Singer, did not return a call Monday seeking comment.

Us said in a statement it stood by its reporting and was pleased with the decision.

The lawsuit stemmed from an article published Oct. 17, 2005, in the magazine's "Hot Stuff" column under the headline, "Brit & Kev: Secret Sex Tape? New parents have a new worry: racy footage from 2004."

It claimed Spears and Federline, feared the release of a secret sex tape, which they had viewed with their estate planning lawyers. The article said that Spears gave a copy of the tape to lawyers and she and Federline were "acting goofy the whole time" while watching the video.

"There was no laughter, disgust or goofy behavior while watching the video in the company of lawyers because they did not watch any video, and because there is no such video," the lawsuit said.

Spears sued after Us refused to issue a retraction.