Jet first appeared in the episode "Jet" of Avatar: The Last Airbender. He and the Freedom Fighters saved The Gaang from a bunch of Fire Nation soldiers. Jet and Katara olbviously had some sort of spark between them, and he was able to lead her astray by telling her a bunch of lies. He managed to get Aang and Katara to fill a damn with water, but when they realised that he was going to kill a whole town of Fire Nation people, Katara froze him to a tree. The damn was still destroyed and the town was flooded, but luckily Sokka had managed to evacuate it in time.
Jet and the Freedom Fighters (minus Pipsqueek and the Duke) next appeared on a ship to Ba Sing Se, he and the Freedom Fighters teamed up with Prince Zuko to liberate food from the Captain for the passangers. After seeing Uncle Iroh heat his tea via Firebending, Jet is convinced that he and he and Zuko are Firebenders (which they are of course). Smellerbee and Longshot believe that he's paranoid, but one night, in the tea shop where Zuko and Iroh work, he attacks Zuko, and the two fight (Zuko using duel swords). Jet is then taken away by the Dai Li, and hypnotized into beleiving that he hasn't been with the Freedom Fighters for a while (P.S. during this time, we find out that the Freedom Fighters are going to Ba Sing Se to change they're ways).
Next, Jet finds Katara in the city, but she attacks him. He keeps trying to convince her that he's changed, and that he hasn't even got the Freedom Fighters anymore. Even when Toph was able to tell that he wasn't lying (or at least, Jet believed he was telling the truth) Katara still doesn't believe him. He helps the Gaang try to find Appa, but when Smellerbee and Longshot see him with the Gaang, they all realise that he's been brainwashed. Katara manages to heal some of the mental damage that had been inflicted upon him, and they all venture to Lake Laogai. They fight the Dai Li there, but when Aang and Jet see that they're leader, Long Feng, is escaping they run after him. Long Feng says that the King has invited Jet to Lake Laogai, and Jet begins attacking Aang. Aang manages to snap Jet out of the hypnotism, but when Jet turns on Long Feng, Long Feng knocks him to the ground via Earthbending. Katara tries to heal him, but she's unable too. Smellerbee and Longshot (Longshot speaking for the first time) tell the Gaang to leave, and Jet tells them that he'll be fine. Sadly, Toph says he's lying.
Bryan Konietzko confirmed at the San Diego Comic Con 2007 that Jet is dead.
Jet is skilled in using Twin Tiger-Head Hook swords.