TMNT: The Next Mutation was a film concept designed to follow up after Teenage Mutant Ninja Turtles III, but it was shelved. The idea behind the film was that the mutagen in the heroes' bloodstream was beginning to change with age, which had effects on them.

• Splinter and Raphael had the ability to transform into giant monster forms.
• Leonardo gained the ability to absorb matter and have his body take on its properties.
• Donatello was losing his eyesight and invented spectacles that actually enhanced his vision to a state superior than originally; he also had minor psychic powers
• Michelangelo could project a human-like visage over himself for covert missions.

The subtitle, although not the concept, was recycled into Ninja Turtles: The Next Mutation