My guess....he was a solider, got paralyzed in battle, got this chance to walk again by going undercover by putting his brain into big blue, whom the humans have been fighting for years, he infiltrates their army, but falls in love with chicky big blue. Tough decisions will be made.
Probably should. From what I've heard, the team developed an entirely new 3-D method for this film. Tarrantino was on set one day messing with the 3-D control panel tablet PC type thing Cameron was using to see shots. He couldn't get over how cool it was.
Friend of mine worked on the movie for about 9 months doing most all the motion capture work and development. Made a boatload of it even though he had to put with Cameron that whole time. He said it's downright impressive what they've done. Cameron even gave him and his crew a role as extras in one of the scenes and they got to dress up in space suit looking things.
Photos I saw from the sets were crazy to see. Green screens everywhere with stuff floating.