Teenage Mutant Ninja Turtles (2012 TV series, season 4)

The Turtles are captured and thrown into the Triceratons' battle arena. Their only chance of escaping is teaming up with a convicted traitor while April and Casey work with the Fugitoid to free them.

• April's inherent psychic powers are beginning to be more developed and grow considerably in strength, due to the crystal fragment of the mystical Sol Star necklace she had received from the Aeons.

The Turtles are transported to a parallel universe, where they meet their counterparts, and together they battle Krang and Kraang Subprime.

• This episode had an early screening at WonderCon on March 26, 2016, one day before its Nickelodeon broadcast date.

Weeks after the Triceratons were stopped, the Turtles now celebrates April's full transition as a kunoichi. They find out Karai has returned and brain worm is gone because she vowed to restore the Foot Clan and undo the damage the Shredder has done to the Clan with the help of her old friend from Japan, Shinigami. It is revealed that Shredder is alive but gravely injured from the previous episode who now uses mutagen provided by Stockman to speed up his recovery and to further increase his strength.

• This episode had an early sneak peek at Comic Con 2016.

When Leonardo secretly allies himself with Karai who now has Foot Soldiers of her own he gets himself into deeper danger than he could have realized, such as Donatello getting injured from explosives and the Turtles and Karai close to death in the Foot Soldier Factory. In the end Karai no longer wants to go after Shredder's belongings but she wants to go after Shredder himself.

• Raphael mentions that he wanted to dress up like a vigilante called "Nightwatcher," a reference to his alter-ego in TMNT.
• Leonardo's costume is a reference to the Foot Ninja outfit that he wore in Teenage Mutant Ninja Turtles when he was magically brainwashed by a witch Kitsume (in the City Falls saga) into believing that he worked for the Shredder.

Donnie experiments with April's crystalline fragment of the mystical Sol Star (which she is becoming quite obsessed with, due to its mighty power further developing and rapidly advancing her innate psychic/extrasensory abilities to tremendously dangerous power-levels), but accidentally supercharges it with electricity that stirs sudden sentience and autonomy in the crystal fragment. It then uses this to bring four of the main characters from Mikey's favorite comic book to life.

For the first time, the Turtles encounter something they cannot defeat - the Super Shredder! Now far stronger and more vicious than ever, Shredder has returned to put an end to Splinter and the Turtles once and for all. He captures Karai and challenges Splinter to another duel to the death. Meanwhile, the Turtles and April have to deal with Tiger Claw, Rahzar, and Fishface.

In the Undercity, the duel between Splinter and Super Shredder begins to heat up; particularly when Shredder's right arm begins to go out of control as a dangerous side effect of the highly unstable mutagen dosages Stockman-Fly had warned him of. The Turtles, April and Karai show up to assist Splinter, but are held up Chrome Domes. As Super Shredder prepares for the final blow, Splinter throws a knife at some smoke bombs, which causes the ledge to crumble and collapse, resulting in the longtime rivals to fall 1,000 feet into the abyss below; presumably to their deaths.

• This episode had an early showing at New York Comic Con 2016.

The Turtles (along with April, Casey, and Karai) desperately hunt for Splinter, as Super Shredder is seen to have survived and has Bebop and Rocksteady make sure that Splinter is truly destroyed. Donnie, Mikey, Raph and Casey go to search the Undercity for Splinter with their grappling hooks; unaware that Bebop and Rocksteady are not far. Meanwhile Leo, Karai and April lure Tiger Claw and Super Shredder to the surface. Leo is separated from the two girls and left to battle Super Shredder all on his own. Fortunately, April uses her extraordinarily powerful telekinetic abilities against Super Shredder and succeeds in saving Karai from being crushed by a truck that contains sulfuric acid (thanks to the mystical Sol Star fragment further amplifying her psionic abilities), her eyes glow a bright blue and she smiles malevolently as she hurls it right back at Super Shredder.

Despite Leonardo's uncertainty, Donatello decides to do tests on April, but only ends up in further increasing her psionic abilities and being possessed by the corrupted spirit of an almighty elder Aeon from within the Sol Star fragment, by the name of Za-Naron. In the end, April succeeds in regaining control, putting an end to Za-Naron and breaking the Sol Star fragment. After recovering from the battle, April apologizes to her friends for not listening to them about the influence the crystal fragment had on her; particularly Donnie, who she nearly destroyed while under Za-Naron's control. She assures everyone that even though she can no longer harness the great mystical power of the Aeons, she now has a better understanding of how to control her increasingly powerful psionic abilities.

• This episode shares some similarities to the four-part "The Dark Phoenix" saga.

Tokka, who is shown to have survived the colossal implosion of the dwarf star in "The Ever-Burning Fire", returns and discovers that her baby boy (whom Raphael adopted as Chompy Picasso) is missing. Determined to get him back, she crash lands on Earth; leading up to an intense battle between her, the Earth Protection Force, and the Turtles who meet up with Bishop, who aids E.P.F. in advancing Earth's defenses against more extraterrestrial invasions. Raph manages to approach Tokka and explains that he only took her baby because he believed that she had perished, leaving Chompy motherless. Touched by this, Tokka leaves Chompy in Raph's care and returns to Magdomar. Splinter wonders what Raph will do once Chompy becomes full grown, to which Raph replies that he knows that Chompy is fated to return to the stars one day but will always look out for him until that day comes.

• This episode aired in South Korea's Nickelodeon on December 17.^{[citation needed]}

A dangerous female assassin and fox-mutant, by the name of Alopex, with super speed, appears who is bent on taking down her own brother, Tiger Claw, with the cursed Blades of Vengeance. The Turtles, April and Casey try to befriend her, but she turns on them and furiously goes after Tiger Claw alone, but not before she curses Casey with the blades. Unfortunately, for her, Tiger Claw has well prepared for her arrival. The Turtles make the scene and distract Tiger Claw while April uses her tanto to break the M.O.U.S.E.R. cage that traps her. In gratitude, Alopex returns one of the blades to Casey, and April uses her telekinetic abilities to borrow Tiger Claw's ice gun so Casey can destroy them, thus breaking their curse. Alopex pins Tiger Claw and seems prepared to kill him again but decides against it as it is not honorable. Tiger Claw shoots her from behind, but Alopex anticipates this and dodges the blast and slices off his right arm; an act that shocks even the Turtles. As Bebop and Rocksteady take the mutilated Tiger Claw away, Alopex takes off to the city rooftops again.

• April uses her extraordinarily strong psychic/extrasensory powers without drawing strength from the mystical Sol Star fragment for the first time. Even though her psionic abilities have been greatly reduced, she is still considerably far much stronger than she was before acquiring the Sol Star fragment.

Guest Star: Minae Noji as Alopex.