Neytiri played by Jim.
Neytiri is a Na'vi princess and a member of the native intelligent species on Pandora.
Jim is a rather gung-ho roleplayer, interested in action, cool fight scenes, and lucrative spoils over careful consideration or puzzle solving. He frequently acts before he thinks, which includes fixating on his own strange explanations for setting details that the GM hasn't explained yet.
Norm Spellman played by Ben.
Norm Spellman is a biologist assigned to study the life forms on Pandora.
Ben is a thoughtful roleplayer who tries to think through the best course of action within his character concept and the setting. He enjoys coming up with clever ways to justify the success of his plans within the premises of the setting.
Jake Sully played by Pete.
Jake Sully is a Marine.
Pete is an old friend of Jim's. Jim invited him along to join in this new game. Pete designed a character to maximise all the skills he thought would come in most useful in a futuristic body-exchange adventure, at the cost of being paralysed and confined to a wheelchair.
Trudy Chacon played by Sally.
Trudy Chacon is a Marine pilot.
Sally is Ben's younger sister. Ben took her along to the game on the first evening when his parents couldn't get a babysitter for the night. The GM quickly gave her a character to play so she wouldn't get bored. She enjoys the make-believe aspect of the game, but has some trouble separating it from reality.
Dr. Grace Augustine played by Annie.
Dr. Grace Augustine is a botanist.
Annie is an acquaintance of Ben's, who attends his drama classes. She was interested to come along and see what this "roleplaying games" thing was all about, after Ben described it to her as a sort of improvisational acting thing. She is dedicated to playing her character as a real, complex person with motivations inspired by a well-considered backstory.
Colonel Quaritch is the commander of the Marine forces on Pandora. His real concern is recovering the mystical Lost Orb of Phanastacoria, a powerful Na'vi artefact capable of making Pandora habitable for humans.
Tsu'Tey is a Na'vi warrior. He keeps an eye on Princess Neytiri and tries to keep her out of trouble, which seems to be a very difficult thing to do with so many human avatars around.
Parker Selfridge is a SecFor administrator. Jake trusts him implicitly, but Neytiri suspects him of some sort of nefarious plotting to wipe out the Na'vi and conquer Pandora. Who is right remains to be seen.
Dr. Max Patel.
Dr. Max Patel is a scientist working on the AVATAR program. He is 38 years old, and uses his great wisdom and popularity to get marines to volunteer to have their brains transferred to cloned alien bodies. How exactly he gets away with this is a mystery.