The character of Lt Dagwood is played by Stargate SG-1 (1997) director Peter DeLuise, and is a tribute to the character he played ('Seaman Dagwood') in the TV series SeaQuest 2032 (1993).
The look of surprised annoyance on Selmak/Jacob Carter's face when Major Davis grabs him on the shoulder (at about 26:50) was genuine. Carmen Argenziano wasn't expecting Colin Cunningham to grab his shoulder that hard, and was rather irritated when it happened, but didn't break character, so the scene was kept in the final cut.
The Goa'uld interior ship set is the completed version of the partially-built set that O'Neill and Martin Lloyd hide from their pursuers in at the studio in Wormhole X-Treme! (2001).
When Col. O'Neill says "excellent" as he sits in the chair on the ship, it is in reference to Mr Burns, from The Simpsons (1989), his favorite show.
Jonas Quinn holds his breath underwater for one minute and 35 seconds while rerouting power (assuming linear time across film cuts).