The Shreddar had a heart monitor implanted in his chest, so that upon his death he would get the last laugh, it would send a drone flying high into the sky where it would release a Mutagen Bomb above New York. October 31st the Ninja Turtles no longer teenagers finally defeated Shreddar once and for all, that day came to be known as Mutation Day or M-Day. Those who were in shelter were fortunate and unaffected, but those who were unfortunate enough to be out in the open were turned into mutants, that included pets, wildlife, police horses/dogs. Ever since M-Day it has been pure chaos in the streets. Animals who were mutated attacked people for food. The mutated humans were ostracized and forced to live in slums or underground. Splinter and the Ninja Turtles began training the various mutants, to give them a purpose, to protect those unaffected by those affected on M-Day.

The United States response to M-Day was to quarantine New York, they destroyed all means of leaving the island by vehicle or foot. Any planes that attempt to leave are shot down and boats are sunk. Any attempts to leave are met with deadly force.