Teenage Mutant Ninja Turtles Season 1 < Free Forever >

: Shredder, Krang, Bebop, and Rocksteady are introduced as the primary antagonists operating out of the Technodrome .

: The Turtles celebrate their 15th "Mutation Day" and visit the surface for the first time, encountering pizza and the alien Kraang . Teenage Mutant Ninja Turtles Season 1

: It features a darker aesthetic with heavy shadows and no pupils in the Turtles' masks. : Shredder, Krang, Bebop, and Rocksteady are introduced

This season transitioned the franchise into with a heavy focus on character growth and humor. Teenage Mutant Ninja Turtles Season 1

: Major arcs include the "Notes from the Underground" trilogy and "The Shredder Strikes Back".