I really need to dig out the Hackmaster

I was reading the latest Knights of the Dinner table, and in it, Brian's mage has a "Chaos Monkey" jumping on his back, interrupting all of his spells.  I'm staring at my 8 unpainted colobus monkeys and "chaos monkey, chaos monkey, chaos monkey" keeps going through my head.  Now I just have to dig out which ever Hackmaster book the Chaos monkey is described...