The surname of Dr. Remy Hadley, played by Olivia Wilde in House M.D., is Hadley. The character is better known by the nickname “Thirteen,” which comes from her number in House’s applicant-selection process.
Hadley joins House’s diagnostic team during the fourth season after he reduces a large group of applicants to a smaller team. Her medical history includes Huntington’s disease risk, and that uncertainty becomes one of the defining personal elements of her character.
Olivia Wilde played Hadley from 2007 until 2012, with periods when the character was absent from the hospital or appeared less frequently. The nickname “Thirteen” is so prominent that viewers may overlook her actual name, Remy Hadley.
Hadley should not be confused with Allison Cameron, another former member of House’s team, or Martha M. Masters, who joins later. The question asks for the character’s surname, not the nickname used by colleagues.