Raph, Leo, Donnie and Mikey emerge from the sewers and tap into undiscovered ninja powers in Nickelodeon's reimagined, 2D-animated series Rise of the Teenage Mutant Ninja Turtles, debuting Monday, Sept. 17. The action-comedy series follows the band of brothers as they discover new powers and encounter a mystical world they never knew existed beneath the streets of New York City.