Zark looks like Zim
Zark when he was young
Is also called Invader Zark.
He was first made when Invader Meen was created. He was supposed to be a replacement for two Irkens, Skoodge and Tak. So they combined Tak and a normal Invader's abilities which brought them Invader Zark. Invader Zark is currently invading Marshmellow-ah. They also added Tallest DNA which may lead to him being the new Tallest.