not sure if you knew this but befroe they did back to the sewer they had 4 seprate concept ideas of what to do.
1 nother season of fast foward
2 turtles participating in some sort of card game
3 turtles return home but because of glitch their younger selves return with them
4 ultimate tmnt would have combined this shwo with the live action movies as well as the original series and the archie comics
its mentioned under wohat could have been under tv tropes