Number Twenty Three is a doctor who helped House a few times when his team had quit.
In Alone. Cuddy sent out a memo telling all the hospital staff not to enable House in an attempt to convince him to get a new team. #23, who had an emergency room patient who shot herself in the leg while high on meth, told House about the memo and originally refused to help House diagnose a patient. However, she let her patient suffer a little, followed House, and helped him by suggesting a combination of crush syndrome and ARDS. She gave House a few ideas, and mentioned that she cared about people. House realized that she had heard that he had a job opening and she wanted the job. He told her to send him her resume. Cuddy and Wilson finally convinced House to hire a new staff.
He hired her along with 39 other applicants. She was the first to be fired, right after she mistook Buddy Ebsen for Neville Chamberlain, even after House promised not to fire anyone who got it wrong.