Thanks for the context, Megea.
"Scatology" is the study of feces. Mieville tells us that they thrived on an intellectual diet of "poop jokes" or jokes and humor about human waste. "Slapstick" refers to silly, physical, violent comedy. "Mimicry", of course, is the act of imitating other people. In this context, the mimicry would be a way of making fun of people.