relationships & decorum on an active military base. The USAF flew up several T-38 Talon, F-15 and F-16 fighter jets to Vancouver for various episodes and direct-to-DVD films. Many of the extras portraying USAF personnel were real USAF staff. Two successive Chiefs of Staff of the Air Force, Generals Michael E. Ryan and John P. Jumper, appeared as themselves in Season 4's "Prodigy" and Season 7's "Lost City", respectively. General Jumper's second scheduled appearance in Season 9's "The Fourth Horseman" was cancelled due to ongoing real-world conflicts in the Middle East. The Air Force Association recognized Richard Dean Anderson at its 57th annual dinner on September 14, 2004 for his work as actor and executive producer of the show and for the show's positive depiction of the United States Air Force. Several scenes of Season 4's "Small Victories" were filmed aboard and outside a decommissioned Russian Foxtrot-class submarine, which had been brought from Vladivostok to Vancouver by a private owner. The United States Navy invited the cast and producers to film aboard the nuclear submarine and at their Applied Physics Laboratory Ice Station in the Arctic for the direct-to-DVD sequel Stargate: Continuum. Themes and allusions Stargate SG-1 takes place in a military science fiction environment and employs the common science fiction concepts of strongly differentiated characters fighting an unequivocally evil enemy (the Goa'uld). However, it links alien races with well-known Earth mythologies, by use of the central Stargate device. Near-instantaneous interplanetary travel allows quick narrative shifts between the politics on Earth and the realities of fighting an interstellar war. Stargate SG-1 gradually evolves the basic premise of the Stargate film into its own unique mythological superstructure, expanding upon Egyptian mythology (notably the gods Apep/Apophis and Anubis as Goa'uld villains), Norse mythology (notably the god Thor as an Asgard ally) and Arthurian legend (notably Merlin as an Ancient ally against the god-like Ori), among others. SG-1 introduces new alien races (as opposed to alien human civilizations) less often than other science fiction television series and integrates newly encountered races or visited planets in stand-alone episodes into its established mythology while leaving the plotlines accessible for new audience members. Despite the show's extensive intergalactic mythology and science fiction elements, scholar M. Keith Booker considered SG-1 ultimately character-driven and heavily dependent on the camaraderie among the SG-1 members. The producers embraced humor and wanted SG-1 to be a fun show that did not