I would place them along the lines of the defamatory pamphlets that rose to great circulation during reformation/restoration. They often involved wood-cuts of well-known portraits, with the faces exchanged with the likenesses of animals (Jean Calvin as a Pig, the Pope as a Wolf) and often gave way to swathes of humorous permutations, which often became popular in-jokes with locals. Furthermore, they were equally easy (and shoddy) to produce and spread quite quickly.

btw, "*chan" within a 1000 word range of "art" is a pretty disturbing thing.