House, Amber Tamblyn House, Amber Tamblyn

There he goes again. Dr. House (Hugh Laurie) has just horrified Princeton-Plainsboro Teaching Hospital's new med student, Martha M. Masters (Amber Tamblyn), with a typically inappropriate question about her sex life. But as soon as the House director yells, "Cut," the looks of disgust on both Laurie and Tamblyn's faces give way to warm smiles. 

"I laugh all day long on this set," says Tamblyn, 27, recalling that Laurie entertained her during a recent children's ward scene by stacking up toy animals "as if they were humping... A cow mounting a chicken; a goat humping a horse. He's just so House-like with the perfect level of darkness. And Hugh does that kind of thing in every scene, which is his brilliance."

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Masters joins the team tonight after a final, fed-up decision by Cuddy (Lisa Edelstein) to get a woman into House's boys' club of diagnosticians, since he has yet to replace Thirteen (Olivia Wilde, who's shooting a film). Thrown into a case of a political campaign manager who may have hepatitis, Masters is at first intimidated by House, who couldn't be less happy to have her foisted on him and isn't afraid to show it.

For his part, Laurie is enjoying having Tamblyn as a new sparring partner. "She's extremely funny," says Laurie, sending an embarrassed Tamblyn fleeing to another set. "She's brought a whole suitcase of gifts to the show; principal among them is her intelligence. She's playing an almost geekishly smart character whose academic life has been a lonely one. Because of that, her teamwork and sense of social skills are not quite what they might be."

Masters — who graduated high school at 15 and has two Ph.D.s already — adds a welcome splash of color to Princeton-Plainsboro's dreary hallways. This day on the L.A. set, Tamblyn, her hair dyed red and cut into bangs, has been costumed in a short denim skirt over orange tights, a butterfly print shirt and platform Pradas. "She also wears a lot of scarves folded into men's neckties to get noticed," says Tamblyn, who equates Masters' quirky look more to Little Edie from Grey Gardens than to Ugly Betty. "She's beyond socially awkward, and we've determined she probably has Asperger's syndrome. She's just all over the place."

And that's something House will naturally prey upon, though Laurie suspects his character sees a bit of himself in this new hire. "I don't think he'd ever own up to it, but secretly there's lots he likes about her," Laurie says. "He loves her intellect and independence. And he gets a kick that she's willing to stare him down." In the tense November 15 episode — when a teenage patient arrives with a potentially lethal contagious disease — the student comes close to outdoing House with her brilliance while getting downright bossy with him.

But because Masters is operating in the hospital without a degree, one of the other doctors on the team always has to supervise, allowing the actress to work closely with Omar Epps (Foreman), Peter Jacobson (Taub) and Jesse Spencer (Chase). "Foreman's still feeling her out," says Epps. "But he likes that she's not yet tainted and is offering a fresh perspective."  

Making sincere apologies, TV's former Joan of Arcadia confesses the odd character is loosely based on her real best friend from childhood, a med student named (yep!) Martha Meredith Masters. Having suggested her friend to producers for inspiration, Tamblyn is now concerned that art might too closely be imitating life. "In my mind, it's an homage," she says, "but Meredith still had to sign off on this, agreeing not to sue any of us."  

Though producers stressed the importance of bringing in Tamblyn to fill the voids left by Jennifer Morrison (now on How I Met Your Mother) and Wilde, Tamblyn has heard her character will stick around after Thirteen returns later this season. "More will be revealed about this character early next year, which is all I can say for now," Tamblyn teases. "There's a master plan for Masters, if you'll pardon the pun."  

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