Bouncing about in a vision of pink, a flouncy skirt, T-shirt and flip-flops, Sandra Oh is entertaining herself on the Hollywood set of “Grey’s Anatomy.” The one-hour drama about the lives of surgical interns is set to return for a second season, and already, in this first week of filming, she is stuck, waaaiting. “It’s so boring, it’s so f-cking boring!” she confides, albeit happily, about the amount of time spent doing nothing on a set. Flopping into a chair, she reacts immediately when a woman remarks that someone smells good.

Grabbing two fistfuls of her cascading curls and sniffing, she says triumphantly, “It’s not me!”

She smells her wrists and repeats herself, then kicks her legs out and starts chomping on a piece of gum, courtesy of a crew member. When she is told that the wrapper is also edible, she looks at the paper in her hand, then pops it into her mouth. It doesn’t dissolve and she makes a face, spitting it out.

“You are so hilarious, you just got me to eat paper!” she says, feigning indignation.

The chewing-gum pusher laughs and insists that it really does work.

Like a Southern hick, Sandra drawls, “I am so stupid. I eat paper ’cause you tell me.”

Noticing a reporter taking in the scene and scribbling in a notebook, she shouts, “What are you writing down?” The reporter laughs.

Like a young girl at her own party, Sandra on downtime is fanciful and fun to watch. According to “Grey’s” co-executive producer and director Peter Horton, there actually was a birthday party for her yesterday, instigated entirely by Sandra herself, who giddily walked on the set announcing the arrival of her 34th glorious year. She even produced two cakes and gathered the cast and crew to celebrate.

“There’s this whole elaborate cheer about how ‘It’s my birthday!’ totally orchestrated by her,” says Horton, who found the whole thing comical and so very Sandra. There is no coyness to her exuberance. Plus, the woman can command a crowd.

“She’s got an energy and spirit to her that is really fresh and unusual,” says Horton.

Those who have Sandra branded to memory as the enraged lover who beat the living hell out of Thomas Haden Church in “Sideways” are learning something new here, as are “Grey’s Anatomy” fans who wonder if Sandra is anything like her aggressive and unapologetic character, Dr. Cristina Yang.

Styling by Jessica Paster @ Magnet, hair by Katy O’Brien, Makeup by Sharon Gault @ magnet

“What I liked about [Cristina] so much is that I thought she wasn’t like me at all,” says Sandra during a brief chat in yet another filming interlude. “I have not played someone who has no sense of humor or someone who is unsympathetic. I really like the fact that she did not come across as sympathetic. More than anything I just wanted to play a good character.”

As she says this, the impish girl who loves birthdays is a little more subdued, but she is not entirely engaged, being somewhat caught up with the prop wheelchair she has chosen to sit in. She can’t help but push herself back, forth, in a circle. Then someone tells her that the caterers are serving meatballs.