Invader Zim: Back In Time! is a 1 hour TV special that aired on Nicktoons on April 10, 2012. The TV special was a huge hit, meaning Nickelodeon might bring back Zim.
Wanting to destory Dib again, Zim builds another time portal to stop Dib from ever being born. However, when he leaves, GIR goes back to the same time Zim became a fake Invader. GIR thinks The Tallest are intruders, so he goes on duty mode and attacks. Somehow, Zim realizes he's not an Invader. GIR goes back to the present year, only to see a path of rubble, fire, and destruction. Now, GIR realizes that HE changed the present which made a terrible one. What's worse, all humans and aliens are slaves to a taller and insane Zim called Future Zim. All of FZ's slaves surrond GIR, and the screen goes black.
Meanwhile, Dib and Gaz find out Zim's plans and go to stop him. However, they see Zim step out of a portal. Realizing that Zim didn't make this dark time period, they go to the Command Tower, only to find GIR being mind drained! GIR attacks Zim, repeating " FUTURE IS MY TIME!!!"
They need the help of Tak to finish this dark future and Future Zim.
As they fight their way through the broken future, they realized the plot of Future Zim is more than enslavement. FZ wants the 5 heroes killed and mangled. Sending out villainous robots and guard dogs, The world seems to end.
In the final battle, Zim and his, "friends", make it to Future Zim's palace. As they fight the tall Irken, Future Zim starts twitching. Two other heads shoot out of his shoulders and his body becomes a giant mantis like-form.
In the end, Future Zim is restored to normal and realizes his bad deeds and becomes good. The story ends with a metallic foot stomping in the dirt. It is likely if there is a sequel, Future GIR will be the villain.