Joi appears as one of the eight chosen acolytes in the Turtles 2003 animated series' so-called "Lost Episodes". Almost nothing is known about her past, but it is hinted that she is by one parental part Japanese. She and her fellow Acolytes, as well as the Ninja Turtles, were deemed worthy enough by the Ninja Tribunal to join the battle against the Tengu Shredder. Her spirit avatar was a hawk, which represents fearlessness.
During a trip to find artifacts that would prevent Shredder's resurrection, Joi appeared to be killed in battle with the Foot Mystics, but reappears later in the season, having mysteriously survived (implied to have been saved by the Ninja Tribunal). However it is a mystery as to how she came back from the dead.
During some episodes, it was hinted that Raphael had developed a crush on her, and even invited Joi to look the Turtles up should she ever come to New York after the battle was over. Joi returned the feelings apparently, telling Raph "let's survive this first, eh tough guy?". The two often fought together, with Raph frequently saving her, as well as avenging her when she presumably died. After this, he said "that one's for you Joi. I won't forget ya'" However, some other episodes implied that she was only staying close to him to piggyback on his efforts, as she did not succeed nearly as much as any of the other acolytes.
Back to the Sewer
Joi's name was initially written as "Choi" on the BTTS character design image. This was later fixed.