(This picture actually has some context with how Zim was imprisoned as you'll see if you continue on, reader!)
Character Name: Zim
Universe of Origin: Invader Zim(More specifically, he's from the planet Irken)
Age: ???
Why they've been imprisoned: After one too many failed attempts at conquering the Earth in the name of the glorious Irken Empire, the FBI/CIA finally took notice of Zim's alien nature after a scuffle with Dib out in the open ruined Zim's totally fullproof disguise which was a wig and a pair of contacts over his normal eyes. It didn't take long before Zim's home was raided by the CIA. In an effort to deny the humans any chance at finding out more about Zim's race or shaming himself even further, he had GIR destroy his computers and the like before the two of them were taken into custody.
Short Character Biography: Zim was just another drone as far as the rulers of Irken, known as the Almighty Tallest were concerned. Just another lamb to the slaughter and another failure. Overly ambitious and eager to conquer the puny and pathetic denizens of Earth, Zim leaped at the chance to try and please the Almighty Tallest by conquering this little blue planet. How hard could it have been? Wanting Zim out of their antennas as they found his eagerness
incredibly annoying and pretty sure he'd screw up one way or the other, they gave him the go ahead he needed. Besides he had already nearly destroyed the Irken homeworld in Operation Impending Doom 1 so sending him on a 'top secret' mission to Earth was the perfect way to get rid of the pest. At least for a while. Of course this was all just a test to prove Zim's mettle as Zim already knew he was the best and simply needed a chance to prove it!
Headed to Earth with nothing but a ship, the PAK that was attached to every Irken child's spine at birth and served as a means of offense/defense and a secondary brain, and GIR-
"DOOM DOOOM! DOOMEY DOOM DOOM!"
"GIR! I'M TRYING TO GIVE THE READERS A BOLD AND DRAMATIC RETELLING OF MY PERILOUS JOURNEY INTO TRYING TO CONQUER THESE GRUBBY LITTLE HUMANS!"
"Oh! Sowwie Big Boss Man!" *GIR skips and hops away*
Anyway, as Zim had been saying he landed upon Earth and quickly forming a disguise/home for himself, he took on the mantle of a human kid and to school with these hairless apes to try and learn more about them, to find out their weaknesses,
SO THEY WOULD INEVITABLY BE CRUSHED UNDER THE IRKEN BOOT OF SUPERIORITY! HAHAHAHAHAHAH!! Hahahha..Ha..You get the idea.
Character Powers: Zim himself doesn't really have powers but he does have aid in the form of:
http://zim.wikia.com/wiki/PAK
http://zim.wikia.com/wiki/GIR
"I suppose if it frees me from this damned confinement, I'll accept your terms." But only so I can conquer you later, humans..MUAHAHAHAHAHA!!!