Turtles Forever 2 is the sequel to the animated film Turtles Forever. It stars the 2012 animated series versions of the Turtles, the 2003 animated series versions of the Turtles, and the original animated series versions of the Turtles.
The 2012 version of Shredder discovers a form of mutagen called electro-mutagen, which can increase the size of molecules and mutate them with mutagen-infected electricity, causing a portal to form. Shredder decides to unite all of the Shredders through the multiverse to defeat the Ninja Turtles once and for all. Shredder manages to bring the 2003 animated version of Shredder and the original animated series version of Shredder into his reality. The Shredders decide to help the 2012 Shredder with his plan to kill the turtles. In the original animated series reality, Dogpound and Fishface arrive and meet with Rocksteady and Bebop. The four mutants use the elctro-mutagen to transport the Technodrome to the 2012 reality. In the 2012 reality, the turtles notice the decreasing gravity. Reports of flying cats, cars, trees, and more come in from all over the globe. The turtles decide to investigate, and are captured by Rocksteady and Bebop. Gravity is also decreasing in the original animated series universe and the 2003 animated series universe. The turtles from those reality are also kidnapped; the original animated turtles are kidnapped by Hun and the Purple Dragons from the 2003 universe and the 2003 turtles are kidnapped by Dogpound and Fishface. All 3 versions of the turtles wake up in the 2012 reality in Shredder's prison. They escape and return to the 2012 turtles' lair, where they meet 2012 Splinter and 2012 April. Suddenly, they are attacked by the original animated series version of Slash, the evil turtle from Dimension X. In the attack, Splinter is severly injured. Slash is defeated, though. The turtles figure out that Shredder's interdimensional transporter is what's decreasing the gravity, and that if he continues to use it everything will eventually float up into space. The turtles return to Shredder's lair, where they are attacked by the 2003 and 2012 versions of Rat King. They defeat both of them, and suddenly the building literally floats up off the ground and into the air. The turtles realize that there is way less gravity and they are almost up in space already. The turtles are suddenly attacked by Hun and the original animated series versions of Tokkah and Razar. They defeat them and enter Shredder's lair where the device is being kept. The three Donatellos figure out how to deactivate it, and the gravity is restored. The building they're in falls to the ground. Back on the Earth, they are attacked by all three Shredders, now combined into the Super-Shredder. After a long battle, they reactivate the machine and push the Super-Shredder into the portal, sending it into an unknown reality. The original turtles and the 2003 turtles return to their home realities, and the 2012 Donatello deactivates it after they leave. Meanwhile, Super-Shredder lands in a reality full of zombies. The millions of zombies attack Super-Shredder as the film ends.
A sequel, Turtles Forever 3: Return of the Shredders, is being worked on by ElectricMayhem.