Jack is a character who appears in the original shooting script of Teenage Mutant Ninja Turtles II: The Secret of the Ooze, with the final date of August 15, 1990. Her role was split between two characters in the final film: Vanilla Ice and an unnamed woman in the audience (Lisa Chess) - the latter of which is only referred to in the script as the "audience man's" date.
Jack is the rapper on-stage when the Ninja Turtles fight Tokka and Rahzar in the film's penultimate battle. She sees the battle and improvises a song titled Ninja Rap.
When Shredder arrives, he holds Jack hostage and threatens to douse her with the last of the mutagen. Donatello turns up the volume of the speaker directly behind The Shredder and Jack, and Michelangelo strums a massive E chord on a guitar, blasting Shredder away from Jack and out of the club as Keno moves her away.
Keno checks to ensure she's okay and she tells him her name is Jack. He asks if it's "like Jackie" and she clarifies that it's just Jack. Keno introduces himself and asks her if she likes pizza, as it is implied the two are going to go out on a date.