Trivia: A G.I. historically refers to an enlisted member of the US Army (and Air Force during the 2nd World War). Lt. O'Neill is in the Navy, where the term doesn't apply. Additionally, she is an officer, so even if she was in the Army she STILL wouldn't be a G.I. Though to be fair, Lt. (Navy) Jane doesn't have exactly the same ring to it.
Trivia: Throughout the film, Master Chief John James Urgayle, played by Viggo Mortensen, reads and quotes poetry. In real life, Viggo is very fond of poetry; in addition to being an accomplished poet, skilled actor, artist, painter, and horseback rider, he published a book of his own poems entitled 'Ten Last Night' before he became well known.