Palladium Books, makers of such reknown RPGs (role playing games) as Rifts, made an RPG based on none other than the Teenage Mutant Ninja Turtles. Written by Erick Wujcik, it was closely based on the Mirage comic TMNT universe, and stayed true to the background established there.
It featured several supplements, one of the highlights called "After the Bomb," which feature the Ninja Turtles in a post-apocalyptic environment in which themselves and other mutants inherit the Earth.
It was a popular RPG, one still sold by Palladium, and has sold approximately 200,000 copies to date. To order yours, simply see the Palladium site order form here.
An extensively revised, updated, and expanded second edition of the TMNT & Other Strangeness RPG, now being titled TMNT & More Strangeness, is being readied by Palladium Books, with new material from the Image Comics series (Volume 3) and Simon Bisley (of Lobo & Body Count fame) art (will somebody remind him that the comic book TMNT do not have different colored bandannas & lettered belts already?). After missing an expected release date of "Fall 1997," then missing another release date of "May 1998," then again missed its scheduled release of "late October or November 1998," was slated for release on January 29th, 1999, was slated for release in "late February," and was yet again slated for release on "April 30th," and currently has a much more broad "late summer 99" release date.
Alas, it was not meant to be. Palladium canned this 2nd edition when sales began to dip in the Image TMNT series during 1999.