Stargate Universe episodes. Amanda Tapping as Samantha "Sam" Carter (Seasons 1–10 main) – A brilliant young astrophysicist and United States Air Force Captain who joins SG-1 under the command of Col. O'Neill in the pilot episode. Following her promotion to Major in Season 3, she is promoted to lieutenant colonel early in Season 8 and assumes command of SG-1. Carter assists Lieutenant Colonel Cameron Mitchell in Seasons 9 and 10. After her appearance in Stargate: The Ark of Truth, she is promoted to Colonel and becomes the new commander of the Atlantis expedition in Season 4 of Stargate Atlantis, before joining SG-1 again for Stargate: Continuum. Carter appears in a recurring role in all seasons of Stargate Atlantis (and as a regular in Season 4) and in the first episode of Stargate Universe as commander of the starship George Hammond. Christopher Judge as Teal'c (Seasons 1–10 main) – A quiet and strong Jaffa alien who defects from his position as the First Prime of the Goa'uld Apophis. He joins SG-1 after the first episode, in hopes of leading his race to freedom. Despite achieving this goal at the end of Season 8, he remains a member of SG-1 until the end of the series. He also appears in both direct-to-DVD films and in Season 4 of Stargate Atlantis as a mentor for Ronon Dex during an interview for the IOA. Don S. Davis as George Hammond (Seasons 1–7 main, Seasons 8–10 recurring) – A United States Air Force Major General (later Lieutenant General) who commands Stargate Command in the first seven seasons. Besides recurring in Seasons 8 through 10 of Stargate SG-1, he appears in Season 1 of Stargate Atlantis. Davis died from a heart attack in June 2008, making his appearance in Stargate: Continuum his last. Corin Nemec as Jonas Quinn (Season 6 main, Season 5 guest and 7 recurring) – A humanoid alien and scientist from the country of Kelowna on the planet Langara. Daniel sacrifices his life (leading to his ascension) at the end of Season 5 in an attempt to save Kelowna, but the following gleeful reaction of the Kelownan leaders causes Jonas to turn his back on Langara. Jonas is a fast learner and fills Daniel's empty spot on SG-1 in Season 6. Following Daniel's return, Jonas returns to his planet and remains a recurring character in Season 7. Ben Browder as Cameron "Cam" Mitchell