How old is the tradition of Purim Torah? The Wikipedia article linked from our PT policy notes a disputed claim of Purim Torah in the talmud (Hulin 139b), with some saying that while the talmud contains humor it doesn't contain the kind of satire that characterizes modern Purim Torah.
I am not asking about Purimspiels (dramatic presentations), though that might be related. What is the oldest case we know of Purim Torah that mimics teaching (written or oral)?