Martha M. Masters

Martha M. Masters arrives at Princeton-Plainsboro as a brilliant, still-in-medical-school outsider drafted onto House's team when he needs a replacement fast. Painfully honest and morally scrupulous, she balks at the lying and boundary-crossing the job requires, and says so, even to House himself. She wants to practice medicine well, and cleanly, if that's possible here.

Masters works because she's the rare House hire who isn't damaged in the usual telegenic way — she's earnest, a little awkward, and genuinely unwilling to bend her ethics, which makes her friction with House feel fresh rather than repetitive. Tamblyn plays her nervous energy and stubborn conscience with real specificity, so her discomfort never reads as naivety, just principle.