Many of the happenings in "Enemy at the Gate" were originally planned because the episode was the 100th episode as well as a season finale. When the writers learned of the cancellation, they found the events even more appropriate to serve as series finale. In writing the episode, the writers had to take a lot of backstory into account. It needed to be addressed that the Atlantis characters did not necessarily know the recurring characters from the Stargate franchise such as Major Davis. Stargate Atlantis was originally intended to be continued by a two-hour movie, but MGM filed for bankruptcy in 2010 and shelved the Atlantis film indefinitely.
