[NES] Teenage Mutant Ninja Turtles - Finale

This is it! The final moment of returning the master Spinter into his original form, just another oldman. I don't remember the story in the live version has this sort of magic spell going on. Why aren't Shredder turning the turtles into human than? Don't laugh, I'm just having some idiotic fun crashing through the enemies just to get by, and shredder being one punch killed in my cheater way.