Jack O'Neill

'''Jonathan J. "Jack" O'Neill''' is a fictional character in the MGM's military science fiction franchise ''Stargate'', primarily as one of the main characters of the television series ''Stargate SG-1''. Richard Dean Anderson played O'Neill in all the ''Stargate'' media since 1997, when he took over the role from actor Kurt Russell, who portrayed the character in the original ''Stargate'' film in 1994. O'Neill and Daniel Jackson are the only two characters to appear in both the original film and all three live-action ''Stargate'' television series.

In his first appearance in the 1994 film as Colonel Jack O'Neill, the character leads the first team to go through the Stargate on a reconnaissance mission. He subsequently becomes the main character of the television series ''Stargate SG-1'' created in 1997 as a sequel to the movie. In the first seven seasons of the show, Colonel Jack O'Neill, recalled from retirement after the first film, is the leader of the team SG-1, a part of the Stargate Program, whose goal is to explore the galaxy and defend against alien threats.

He became less prominent in the eighth season, in which he is promoted to Commanding Officer of Stargate Command, at the rank of brigadier general, therefore greatly reducing the character's time spent exploring via the Stargate. Anderson chose to spend more time with his family, eventually leaving the show at the start of its ninth season and only appearing four times until the end of the series in its tenth and final season. The character's absence from the show was explained by yet another promotion, to the position of head of the Department of Homeworld Security, as a major general.

Anderson reprised his role once again in the direct-to-DVD film ''Stargate: Continuum'', a sequel to the TV series. O'Neill also appeared in the two other ''Stargate'' television series: he was an occasional character in the first three seasons of ''Stargate Atlantis'', serving as an Earth contact with Atlantis, this running parallel with Stargate SG-1 for a time, and in four episodes of ''Stargate Universe'', as a lieutenant general, having been promoted sometime after both ''SG-1'' and ''Atlantis'' had ended. His appearance in this show's first season finale is his last appearance in the ''Stargate'' universe to date. Anderson also voiced the character in the video game ''Stargate SG-1: Unleashed''. Provided by Wikipedia