Jenny McCarthy, New Year's Rockin Eve Jenny McCarthy, New Year's Rockin Eve

Jenny McCarthy says "all bets are off" when she co-hosts Dick Clark's New Year's Rockin Eve with Ryan Seacrest this time.

"[I'm] literally winging it," McCarthy tells "What I learned from last year was that I don't need to prepare as much as I thought I did. The cameras go on, they yell at you in your [ear piece] and all bets are off ... if I'm having fun everyone else is having fun."

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McCarthy, 39, will return to New York City's Times Square, but this year's countdown show will be extra sentimental with a two-hour prime-time special marking the program's 40th anniversary. "That's a bit of nostalgia viewers will get to experience," she says.

And there's of course the heart-tugging aspect of the 82-year-old Clark, who started the show, himself continuing to anchor the countdown show in the wake of his stroke several years ago.

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Among this year's lineup of performers are Lady Gaga, Justin Bieber, Pitbull and Hot Chella Rae. McCarthy says she's most excited to see what Gaga is going to wear. And Bieber? "I'm sure all those kids that can't go out on New Year's Eve will have so much fun watching him perform," she says after a pause.

New Year's Rockin' Eve: The 40th Anniversary Party airs Saturday at 8/7c on ABC; Dick Clark's New Year's Rockin' Eve with Ryan Seacrest then airs 11:30/10:30c. In between there's Dick Clark's Primetime New Year's Rockin' Eve with Ryan Seacrest at 10/9c.