The season arc centers on the new threat of the Ori, a race who Daniel Jackson (Michael Shanks) and Vala Mal Doran (Claudia Black) unleash in an unknown galaxy, and who are threatening to prepare for a crusade into the Milky Way galaxy to convert the beings to their religion called Origin.

Season nine regular cast members included Ben Browder, Amanda Tapping, Christopher Judge, with Beau Bridges, and Michael Shanks.

Since the environment of Vancouver, British Columbia, Canada, where SG-1 and Atlantis were primarily filmed, was being developed, shooting locations were getting rarer for new offworld stories.

Ben Browder and Beau Bridges joined the main cast in Season 9, as Cameron Mitchell and Hank Landry, respectively.

Richard Dean Anderson had left the main cast after Season 8 to spend more time with his young daughter in Los Angeles.

[3] Despite being listed in the cast credits for the whole season and short scenes in Avalon (Part 1), Amanda Tapping as Samantha Carter is absent during the first five episodes as she was in the last stages of pregnancy at that time.

Her empty spot was filled by guest star Claudia Black, who would leave in "Beachhead" and return for the last two episodes of Season 9, which involved her real-life pregnancy.

[4] The title of the episode "Ex Deus Machina" is a hyperbaton of "deus ex machina" (literally "God out of a Machine", meaning "God appearing on a crane", a literary device for a kind of turn of events) after he jokingly suggested to his writing partners a plot about Ba'al working undercover as a mechanic on Earth.

A review in TV Guide Special #67 considered Mitchell's introduction in "Avalon" still too reminiscent of the production team's own efforts to turn around the Season Eight finale.

"Origin" was nomininated for a Gemini Award in the category "Best Achievement in Make-Up", while both "Beachhead" and "Camelot" were nominated for "Best Visual Effects".