LOL! Once again, the Doctor hits the nail on the head. The joke is funny, talking about how funny the joke is (like MP did, decades ago), is funny. Referring to how MP talked about how funny the joke is (like the Doctor is doing) is funny. Referring to *that* (like you are doing), is funny. Pointing how how funny *that* is (like I am doing), well, okay, maybe it only goes so far.