Most interestingly, the movie was intending to feature the turtles undergoing a second mutation, linked to the characters aging. This would have allowed the team to develop different powers, change slightly visually, and have further issues to contend with as they get to grips with their alterations. Naturally, it would have also been a logical way to sell more toys, with any action figure from past movies becoming outdated thanks to the upgrade in design.
Character Concept Art
We also know of some of the other characters that would have been included in the sequel. Thanks to additional concept art of the movie, drawings were produced for characters like Fang, Shredder, Spyder, Nano Spyder, Kasey, Talbot, Bugman, and Evil April. That list of names should give a general idea of new and returning villains while the story would have clearly seen April corrupted and perhaps even betray the group. The idea that April might have served as some form of antagonist does suggest that the narrative was moving in a lot of different directions, hinting that the original premise might have been overstretched, especially if she too got splashed with some ooze.
The mention of Spyder and Nano Spyder appeared to be original creations for the movie, suggesting again the film was departing from canon in its bid for an imaginative story. The concept art here strongly implies that Nano Spyder might have been an upgraded iteration of Spyder, with the villain perhaps morphing to contend with the newest turtle abilities. In the years since, the concept behind the foe has never been recycled, implying that there wasn’t anything particularly memorable about the new creation.
On top of this, the return of Shredder added yet another villain to the project, with his surprising comeback in spite of his previous fate linking to The Foot Walks Again title. The character would have been rebuilding The Foot to its former glory, adding to that pre-existing rivalry. Just like Spyder and the turtles, Shredder was supposed to be upgraded into Super Shredder. This picks up on the ending of Teenage Mutant Ninja Turtles II: The Secret of the Ooze (1991), and is an idea that has been played with on the small screen where Shredder occasionally evolved to be even more menacing.
Considering concept art had already been put into production for The Foot Walks Again, it might come as no surprise that a script had actually been created for the piece. In fact, three scripts are known to exist from the production, which may account for the various villain choices and alternative titles. The first was written in 1995 by Christian Ford and Roger Soffer (writers who would go on to pen the Shaquille O’Neal-starring Kazam in 1996). The second was a rewrite of this draft in 1996 by Craig Shapiro and John Travis. The final version was a new draft from the latter two submitted in 1997.
It could be that what we know about the cinematic outing is a result of the combination of these various scripts. Therefore, it might be that all of these diverse elements were never intended to be balanced in a single film.