An, apparently, insane artist or intellectual. They would be labeled 'eccentric' or 'mad' by most. They tend to spend a lot of time alone and think a lot.
That one neighbour that never leaves home and eevryone thinks is a vampire, is probably a madnick...or a vampire;
'Pinky and the Brain' - Brain is a madnick;
Evil Genius 2 (PC) gave us the opportunity to play a madnick; and basically, most of everybody who ntries to take over the world