I got the idea when I saw a interpretation of Valerie Solanas SCUM manifesto by the Swedish theater group "Turteatern". The men had to sit on rather uncomfortable chairs while the women sat on comfortable cushions. The play is rather controversial (the actor had to live under police protection for a while since some men where unable to appreciate the satiric humor). I think it was rather funny. In any case - the "Pacman scrotum crusher" idea popped into my head after watching this play.
I don't know if I need to explain how I did it, it seems rather obvious :). Use a IKEA FROSTA stool. Just cut of a slice using a saw, then paint the edges and make an eye.