Stargate SG1

While Richard Dean Anderson was the biggest name starring in the original series, Michael Shanks starred in the original movie as Daniel Jackson. The part of Col. Jack O'Neil was played by Kurt Russell, who did a wonderful job I might add. Samantha Carter played by Amanda Tapping, and Teal'c played by Christopher Judge rounds out the original SG1 team.

Who could replace Jack? No one that is why they created a new character to lead the team and keep The Jack O'Neil character alive. Lieutenant Colonel Cameron Mitchell ( Ben Browder ) gets the team back together SG-1 team's off-screen separation after the previous season. Another addition to the team was Vala Mal Doran (Claudia Black) who was created by Damian Kindler and Robert C. Cooper as a guest character for the season 8 episode "Prometheus Unbound" (2004). The on-screen chemistry between Vala and Michael Shanks' character Daniel Jackson, and the character's popularity with the producers and the audience, Claudia Black became a recurring guest star in season 9 (2005-2006) and joined the main cast in season 10 (2006-2007).

The Ori are a group of "ascended" beings who use their advanced technology and knowledge of the universe to attempt to trick non-ascended humans into worshipping them as gods.
They first appeared in the ninth season of Stargate SG-1, replacing the Goa'uld as the show's primary enemies.

The producers had grown creatively tired of writing endings.They had good experiences with the first season of Stargate Atlantis, so the producers decided to revamp the series in more fronts than just adding new characters by introducing new villains and new missions. Thus they considered the beginning of Season 9 as the pilot of a new show.