Title: Timothy McGee
Content:  Timothy Farragut "Tim" McGee    is a fictional character from the CBS television series NCIS. He is portrayed by Sean Murray. McGee specializes in cybersecurity and computer crime, and is a graduate of Johns Hopkins University and MIT. Murray appeared as a guest star in eight episodes of the first season of NCIS; in season two he joined the main cast and was added to the opening credits.
Title: Timothy McGee
Content:  to have little experience in using weapons compared to his colleagues (Tony was a cop, Gibbs was a sniper, Kate was previously in the Secret Service while Ziva was a highly skilled Mossad operative). In Season 11, with the transfer of Ellie Bishop from NSA to NCIS, McGee has begun to assert to seniority. He used some of Tony's old pranks on Bishop, such using a trick coin when tossing to see who has to retrieve a corpse from a septic tank. In the Season 13 finale episode, "Family First", with DiNozzo having resigned from the team for good, McGee is promoted to Senior Field Agent.
Title: Timothy McGee
Content:  possible murder of a Navy Petty Officer and let him decide whether to call an investigation. He let McGee accompany him into the interrogation room while still a "probie" and allows him interrogate a suspect alone as early as the Season 3 episode "Deception". McGee is always shown as a computer consultant to Gibbs. Ziva has had a friendly relationship with McGee since her start at NCIS. It resembles one of brother and sister. While Ziva teases McGee a great deal, often with Tony, they remain on friendly terms (Ziva's teasing is far more playful than Tony's, who takes a much more sadistic approach to the pranks 
Title: List of NCIS characters
Content:  Timothy "Tim" McGee (Sean Murray) first appears in the episode "Sub Rosa" as a case agent stationed at Norfolk, and is promoted to field agent and assigned to Agent Gibbs' team at the end of the season two premiere, "See No Evil", becoming a regular character. He serves as a field computer consultant and occasionally assists Abby in the lab. McGee clashes with DiNozzo, though after the two became partners (following Ziva's departure from the team at the end of season six), they are frequently shown to form an effective team; however, their relationship has occasionally reverted to its original state upon Ziva's return. McGee's methods are often indecipherable 
Title: Timothy McGee
Content:  Timothy McGee has green eyes and brownish-blond hair. He was overweight until the end of season 6; during the seventh season, he was shown to be losing weight. When DiNozzo pesters him about it, McGee replies that he has lost 15 pounds. McGee's weight loss led to speculation that Sean Murray, the actor who portrays McGee, was ill; in October 2010 Murray, via his Twitter account, explained that it was a deliberate weight loss via dieting, consuming only organic food and abstaining from alcohol and sugar. Murray has lost 25 pounds. In his initial appearances, McGee always wore a suit, dress shirt and a necktie. From season 4, he stopped wearing neckties and adopted a slightly more open-collar look. From season 7, he began frequently wearing leather jackets and bomber jackets over his shirt. For the first 14 seasons, McGee had a clean-shaven appearance; during his time being held hostage in Paraguay between seasons 14 and 15, he grew a beard, which he has since kept since his return to NCIS.
Title: NCIS (season 3)
Content:  Viewers       = 18.17 ; ShortSummary  = While the team is on protective detail for the Chief of Naval Operations, McGee spots an argument taking place in an alleyway. He shoots one of the men, who he believed was aiming a gun at him. The deceased turns out to be a D.C. Metro police detective who was working undercover. When the team is unable to find any weapon or bullets left behind by anyone other than McGee, it appears that McGee may have made a probie mistake. McGee begins to doubt himself but Gibbs is suspicious of the detective's meeting, which took 
Title: Timothy McGee
Content:  The character's seeming inexperience in the field during early seasons was noted by critics, with Bill Keveney of USA Today describing him as "a wet-behind-the-ears computer expert" in 2005. A few months later, Noel Holston from Sun Sentinel styled McGee as the "newer, nerdier agent" of the group. In 2007, television historian Tim Brooks described him as "the earnest, conservative probationary agent with invaluable computer skills who was often the victim of Tony's pranks". The Daily News referred to McGee as "the requisite tech wizard" of the show. Alyssa Rosenberg from The Washington Monthly suggested that the characters of McGee, "an MIT-educated geek who writes thinly veiled novels about the team", and Abby Sciuto appear as "liberal stand-ins" in contrast to more conservative figures on NCIS, such as Gibbs and Tony DiNozzo. None of the characters' political views are specified within the series, and Rosenberg stated that, as a result, the show does not "demand that the audience take sides in divisive issues".
Title: Timothy McGee
Content:  McGee was born in Bethesda, Maryland, on September 13, 1978, to an Irish American family. He spent his childhood in Alameda, California, as his father was a naval officer stationed there. His parents bought him his first car—a 1984 Camaro Z28 5-speed—the day he turned sixteen. However, he crashed into a bus while trying to figure out how to use the windshield wipers. He got a student pass the day he got out of traction. He earned a Bachelor of Science degree in biomedical engineering from Johns Hopkins University and a Master of Science degree in computer forensics from MIT. His college GPA was 3.9, as he failed a fencing class in his sophomore year. He worked at the NCIS field office in Norfolk, Virginia, before being transferred to the headquarters in the Washington Navy Yard, a move made permanent at the end of the season two episode "See No Evil." McGee has a younger sister, Sarah, who is played by Troian Bellisario (Murray's stepsister in real life). Sarah attends Waverly College and intends to be a writer like her older brother.
Title: Frank McGee (journalist)
Content:  Frank McGee (September 12, 1921 – April 17, 1974) was an American television journalist, best known for his work with NBC from the late 1950s into the early 1970s.
Title: NCIS (season 8)
Content:  source of a number of computer hackings to NCIS. This makes McGee nervous as he had regularly illegally hacked into government computers under Gibbs' orders. The team manages to track down Maxine (guest star Beth Riesgraf), who is the dead Marine's girlfriend and is an avid gamer and computer expert. She begins to take a liking to McGee. However, McGee tries to maintain his distance due to the events in "Defiance". She reveals that she had accidentally uncovered some sort of encrypted code in an MMORPG which turns out to be a program capable of hacking the Pentagon. The team 

Question: when did mcgee became a regular on ncis?
Answer: in season two.
season two.