Wouldn't a game made from that show technically belong to that creator or owner of the show? Might there be like copyright issues? Hmmm, now that's got me wondering.
I think technically you would need to at least get permission from the company that owns the licensing. Of course, if you were able to contact the intellectual copy right owner (gold ole vasques) you may be at least able to get permission to use his art work/characters without direct licensing permission. Something to look into for anyone who really would like to make a game based on zim.
copyright laws won't go into flare as long as you put your own flare into it. For instance, PPG doujounshi on snafu-comics.com and a fighting game on flashportal. Those weren't sued.