Unusual for a series, Showtime ordered forty-four episodes (a second season) before showing the pilot. Halfway through the first season, they ordered another forty-four episodes.
Christopher Judge (Teal'c) and Amanda Tapping (Samantha Carter) are the only cast members to stay with the series throughout its entire run and, consequently, to appear in 200 or more episodes.
Although the SGC is a fictional location, its home base at the Cheyenne Mountain Complex is an actual Space Force installation belonging to the Air Force at the time of this series. The exterior shot of the main entrance tunnel to the mountain base is the actual entrance, and the blast doors (seen closing in any episode which features the SGC going into Lockdown) do exist at the facility in real life.
The character "Jack O'Neill" was ranked number ten in TV Guide's list of the "25 Greatest Sci-Fi Legends" (August 1, 2004 issue).
Stargate SG-1 and its spin-offs are the only television series endorsed and supported by the United States Armed Forces, particularly the Air Force Space Command (the predecessor to the modern-day U.S. Space Force).
Martin Wood: multiple cameos throughout the series, most of which were uncredited, non-speaking roles. Several of them involved him and Dan Shea (Siler) standing in the background holding a large over-sized adjustable wrench.
Peter DeLuise: multiple cameos throughout the series, usually uncredited roles as background characters.