<P> Special Agent Caitlin Todd is a fictional character featured in the CBS television drama NCIS . She was portrayed by Sasha Alexander, who appeared in 49 episodes of the series . Alexander made her series debut in the season one premiere "Yankee White", before departing the regular cast in the season two finale "Twilight". Alexander was credited as a guest star for her appearances in the season 3 episodes "Kill Ari (Part I)" and "Kill Ari (Part II)," and appeared uncredited in likeness and in voice during season 8's "A Man Walks Into a Bar". Subsequently, Alexander has appeared in photographs, flashback, and CGI footage, most recently in "Family First" (season 13). </P> <P> Following JAG's "Ice Queen" and "Meltdown", the character of Kate was created to replace that of Vivian Blackadder (Robyn Lively), who Donald P. Bellisario felt was "too soft". Alexander credits CBS President Les Moonves with her casting, stating that she "had just finished doing a couple of other series for CBS and he said,' come do this show"'. </P> <P> Donald P. Bellisario stated that Alexander departed the series due to a lack of stamina and grueling filming schedule, stating "this was the first time (Sasha) went over a year on a show". Co-star Michael Weatherly noted that he was not informed until February 2005, and only discovered Caitlin would be assassinated when he "saw the special - effects guy attaching a blood pack to (Sasha's) hair". Alexander does not regret leaving the series, "for a million reasons that I've never spoken out about...for a million reasons that I can't". Following Caitlin's death, fans "flooded Internet message boards with angry postings directed at Bellisario", while Bellisario announced that Alexander's replacement would be "a new female lead character (...), quite different from the conservative Agent Todd . A' European or Australian girl who is very comfortable with her femininity and sexuality"'. Chilean actress Cote de Pablo was later cast as Israeli Mossad Officer Ziva David to replace the departed Alexander . </P> <P> Caitlin was born in Indiana, and was the youngest of five children, including three brothers (whom she referred to as "practically psychotic"), and an elder sister (introduced as Rachel Cranston in Season 8 Episode 14 "A Man Walks Into a Bar ..."), and was Catholic . She also mentioned having a cousin named Maureen Ingalls . </P>

Who came first on ncis kate or ziva