It looks like Sean Penn has made a lightning-fast rebound from his recent breakup with wife of eleven years Robin Wright Penn -- and taken his onetime "Hey, bud, let's party" catchphrase to heart.

The ornery actor, 47, was uncharacteristically smiley -- heck, he even showed teeth -- as he hit the weekend Oscar festivities with tsunami-surviving model Petra Nemcova, 28, whose spotty romantic history includes an interlude with unlikely lothario James Blunt and a flirtation with Bruce Willis.

Petra and Sean at Elton John's Oscar afterparty

The pair turned up together at Elton John's Oscar soiree, where they posed for pictures and got up close and schmoopy.

"They were canoodling all night," an eyewitness tells the New York Daily News. "He looked like a high school boy in love. Petra was taking photos of them together on her cell phone."

Another spy tattles that Sean kept his digits firmly planted on Petra's posterior while on the dance floor (he dances? Who knew?), observing, "It was a very proprietary gesture."

The New York Post adds the newly minted amours held hands and "snuck kisses for hours."

Penn even let his newly dark brown hair down during a favorite ditty.

"He was so happy and was singing along and dancing with her to 'Philadelphia Freedom,'" a fellow attendee marvels to the Los Angeles Times. "It was like, 'Is that Sean Penn?' I've never seen him act that happy in public."

Sums up a source to FoxNews.com, "It was a total love fest. Penn and Petra totally looked like they should have gotten a room. Sweet but sickly."

Before popping up at Elton's shindig, Penn and Nemcova were reportedly seen looking thisclose at a CAA bash and at hot spot Villa.

The statuesque model, however, will only go so far as to confirm they're pals.

"Yes, we are friends," she sidestepped to People. "He is on the advisory board of my charity."

As for Penn, he was supposedly a bit more forthcoming about Petra. According to the London Daily Mirror, he was eloquently overheard declaring that she's "totally [bleeping] cool."

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