My favorite characters in my game I never finished: Pandiction. It was a sidescroller maze game.
3 and 4, and 6 and 7 are the same people, just zombified. Not too worried about color count. Cause it doesn't matter that much for games. But theres only 2 shades of red :p
Also, a quick thanks to Jeremy for his advice on making my last peice transparent. Unfortunantly it didn't make it in time for the contest. | 
Glad you asked. They were originally invented by my younger brother's friend. I personally see them as semi-violent robotic people. But the first two are not robots. Just a skeleton and a zombie.
EDIT: Added more of the characters to the set. Forgot about a few of them :o