The U.S. military Defense Condition (DEFCON) system actually counts down from five (normal peacetime operations) down to DEFCON 1 (maximum readiness for nuclear war), despite the film's title implying DEFCON 4 was reached during a full-scale nuclear war. DEFCON 4 is actually only being slightly more prepared for war than a standard peacetime defense condition. The highest confirmed DEFCON was DEFCON 2, during the Cuban Missile Crisis.
A film infamous among sci-fi fans for misleading artwork, as the painting used on the poster and video/DVD boxes bears no resemblance to anything that occurs in the actual film.
A Canadian Social Insurance Number (SIN) card is used as part of a tripwire for the trap on Vinny's farm that explodes approximately 30 minutes into the film. It is the real SIN card for Cordell Wynne, line producer for the movie, which reveals that his middle name is 'Gerald'.
The Nemesis mission is a joint Canadian-US space station, as evidenced by the Canadian and American flags on the space suit that Capt. Walker wears for a repair spacewalk.
Dr. Eve Jordan appears to be a civilian as unlike the other crew she is never referred to by a military style rank.