Sasha Alexander (born May 17, 1973) is an American actress of Serbian ethnicity. She is known for her roles as NCIS Special Agent Caitlin "Kate" Todd (Caitlin Todd) in the first two seasons of the CBS television drama NCIS (NCIS (TV series)), a minor role as Melissa in Mission: Impossible III (2006), as Lucy in Yes Man (Yes Man (film)) (2008), and as Catherine in Hes Just Not That Into You (Hes Just Not That Into You (film)) (2009). She also had a guest appearance as Nora in the episode The Down Low (The Down Low (House)) of the TV-series House (House (TV series)).