The series adapts a large scope of story arcs from the comics, with the Turtles' adventures combining elements of both fantasy and science fiction.

Halfway through the season, Leonardo is approached by the Foot Clan leader Oroku Saki, later learned to be The Shredder, who funded Baxter's Mouser project and is Hun's master.

When the Turtles return to New York they confront the Shredder once more and Master Splinter goes missing, leading to the introduction of the Utroms, an alien race secretly living on Earth.

This season also introduces Karai, Shredder's daughter and pupil, when she comes to take control of New York during a gang war.

Agent John Bishop, leader of the Earth Protection Force, is introduced as an independent antagonist fighting both the Turtles and the Foot.

Season Four sees the Turtles recovering from their final battle with Shredder, particularly Leonardo who suffers from post-traumatic stress disorder.

Karai takes leadership of the Foot, Hun leaves to reform the Purple Dragons into a powerful crime syndicate, and Bishop stages a faux alien invasion to secure funding for the EPF.

During this season, the Turtles go through many trials and tribulations on their journey to become the best fighters they can be, eventually tapping into ancient energy to defeat the original Shredder.

They must also contend with futurist enemies like Sh'Okanabo and his minion Viral as well as dealing with the activities of Cody's greedy and ambitious uncle Darius Dunn.

[12] Teenage Mutant Ninja Turtles received widespread acclaim and was commercially successful throughout its first five seasons, receiving wide critical praise for the faithfulness to the source material, the storytelling, character development, action, darker tone, humor, the theme song, background music, voice acting, animation and appeal to all ages.

[citation needed] It also garnered high ratings for a 4Kids Saturday morning cartoon and shortly after the premiere became the highest-rated and most popular children's television show in the US.

[citation needed] 4Kids was known for its controversial history of censoring anime, but the series was acclaimed for trying to follow the dark and gritty tone of the original Mirage comics.

[13] However, due to 4Kids having to keep their ratings under PG, the last two seasons of series, Fast Forward and Back to the Sewer, was met with negative reception from fans and critics alike.

Angel, Ch'rell, Darius Dun, and the Street Phantoms would also be featured in the IDW comics, and the Triceraton Mozar as an antagonist during season 4 of the 2012 series.