The concept art from the fourth TMNT movie that never was gives us a look at fifth turtle, Kirby
The next TMNT movie that Michael Bay has a hand in-- happening, not happening, in limbo-- whatever the case, I can tell you that TEENAGE MUTANT NINJA TURTLES IV: THE FOOT WALKS AGAIN will never be anything other than a couple of scripts and some pages of dated concept artwork.
Currently up for sale at Heritage Auctions is that batch of TMNT 4: The movie that never was. Below you will see a few pages of concept art including Casey Jones with electric powered fists, Super Shredder, and the fifth turtle, Kirby (love the colors on the art). Co-creator of the TMNT, Kevin Eastman did the drawings, which aren't bad, but a little out there concept-wise. Hey, I think we've all seen crazier shit... "The fourth live-action TMNT film was pitched and originally scripted as a grittier, less kid-friendly adventure, and to that end Kevin Eastman designed a more brutish, hardcore fifth Turtle, named for the legendary King of Comics (Jack Kirby)."
Kevin Eastman Character Designs for Unfilmed Fourth Teenage Mutant Ninja Turtles Movie Original Art Lot of 25 (1995-97).Many of these 14 pieces also have art on the backs, for a total of 25 pages of art! Many are devoted to Kirby, the fifth turtle, but also featured are Fang, Shredder, Spyder, Nano Spyder, Super Shredder, Kasey, Talbot, Lawson, Bugman, and Evil April. Each piece measures 8.5″ x 12″. All are rendered in pen, with one color piece in watercolor and the others in marker.
There's a ton more (Evil April nips included), so to get access to all of the pics head on here. It takes all of a minute to sign up, plus give you access to the other auctions.