On the Prometheus, Mitchell tells the 'other' SG-1 that "you must be okay, you're not wearing beards." This is a reference to Star Trek (1966) Mirror, Mirror (1967) which also explored the concept of parallel realities. In the parallel Star Trek universe, the alternate reality crew tended to be more antagonistic and Spock, most notably, had a beard that distinguished him from his counterpart.
After Kvasir leaves the Prometheus, Daniel Jackson, played by Michael Shanks, says, "I miss Thor." Shanks voices Thor.
One of the alternate Carters is a "nerdier" version wearing the same thick rimmed glasses as the Dr. Samantha Carter in Moebius: Part 1 (2005).
Episode director Peter DeLuise appears as a uniformed airman in the background of the base commissary. He is visible over Carter's shoulder during the scene at around 21 minutes into the episode.
Regarding the Asgard, Mitchell tells Carter he would have expected pants. Coincidentally, later in the episode, Mitchell is also without pants.