the ubuesque

In the lecture course Les Anormaux, Foucault uses a category he calls 'the
grotesque' and compares it to one he calls 'the ubuesque' (p. 12). This word
apparently dates from 1922, and a book called _Ubu roi_. French dictionaries
suggest that it describes someone who by their grotesque, absurd or cruel
character resembles 'Ubu roi' (p. 26n. 20). Any idea who this person was,
and if they were really a king?

Hope someone can help

Thanks

Stuart