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This week's tabloids present … Robert Pattinson and the cryptic case of the mystery brunette. Over the weekend in Los Angeles, the actor, whose fickle romance with Kristen Stewart hit the skids (again) in May, was spied cozying up to an unknown, dark-haired lady during a birthday bash for his pal, Shoshana Bush.

Us Weekly says Rob, 27, looked "really happy" as he held hands and danced to Frank Sinatra tunes poolside with his unidentified date, who was "heard calling him 'babe.'"

"There were like 40 people at the party -- it was intimate -- and Rob was next to her the entire time no matter where he was," says a source, who seemed to find this Bella-and-Edward-esque joined-at-the-hip action romantic rather than stifling and awkward.

"Rob and the brunette turned up around midnight. They were cute together," another spy adds to Radar Online. "At one point, he was talking to someone and she wandered over and grabbed his hand and pulled him to over to near the pool. Their hands were all over each other!"

In between the PDA, she apparently made a good impression on Pattinson's pals.

"She's really sweet and [has a] girl-next-door vibe," opines the snitch. "Rob is actually really nice and humble. They're a perfect match!"

Three days later, Pattinson was snapped with a pretty brunette as he left a gym, with the pair saying their goodbyes and hopping into separate cars. Same woman?

Not according to E! News, which IDs the shapely looker as the actor's trainer, who is helping him get in shape for his role in the forthcoming "Mission: Blacklist."

Meanwhile, Life & Style confuses matters further by claiming Rob stepped out on Sept. 7 with Dylan Penn, the blond, 22-year-old daughter of Sean Penn and Robin Wright.

They supposedly hit the Viper Room, where "they were touchy-feely and very flirtatious," according to a spy. "There was a level of comfort there. You could tell they've hung out a few times."

Chances are Papa Penn would strongly discourage that attachment, given his longtime loathing of the paparazzi, who are constantly circling Pattinson.


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