The comment by "Colonel Danning" in the Wormhole intro, "Yes, it does say Colonel on my uniform," is a reference to an earlier episode where Jack O'Neill, after being argued with by the rest of SG-1, says, "Does it say Colonel ANYWHERE on my uniform?"
The studio where Wormhole X-Treme! is being shot, Bridge Studios, was also the primary filming location for the series.
Wojciech Jakubowski (Polish underground actor) was actually on his vacation in US and was invited by his friend to see the set of Stargate SG-1 (1997). When Peter DeLuise saw Jakubowski, he was struck by his 'soldierish' look and asked if he wouldn't play a soldier in The Tomb (2001). Jakubowski agreed and both men liked the co-operation so much, that he played in two more episodes - Wormhole X-Treme! (2001) and Proving Ground (2001).
A shot that didn't make the final cut was Hammond and SG-1 watching the preview of Wormhole X-Treme! where all sit watching in silent disbelief, except for Teal'c who bursts out laughing at the sight of Grell.
Martin Lloyd remarks "The real money's in syndication." while he and Jack are being rescued by Teal'c. It is generally known in the television industry that you need at least 100 episodes for a show to be considered seriously for syndication. This was the 100th episode of Stargate SG-1 (1997).
Joseph Mallozzi: (writer) as the man trying to get a doughnut from Teal'c. The man beside him (in the purple shirt) is producer N. John Smith.
Michael Greenburg: (executive producer and Richard Dean Anderson's partner in Gekko Film Corp.) as one of the two random guys (the one with longer hair) looking up at the spaceship at the end.
Robert C. Cooper: (lead writer and executive producer) plays the writer on set who Martin scolds, "Go write something!". His name is also briefly seen as the author on the cover of the book "Dust off that old Screenplay and Sell it!" being read by a security guard played by Laura Drummond.
Brad Wright: (executive producer and co-director) as one of the two random guys looking up at the spaceship at the end.
Peter DeLuise: appears as the Director of the fictional Wormhole X-Treme! DeLuise is the director of 57 Stargate SG-1 episodes.