My friend told me about her brother-in-law who seems to not understand jokes at all, even the simplest, most obvious ones. She finds herself making even more jokes than she might have otherwise, because his behavior is so baffling.
I would absolutely do the same. When I encounter someone as literal as my friend’s brother-in-law, I become a compulsive joke maker – somehow convinced it is my delivery not his absolute-ness. It’s a recipe for feeling very foolish when, in fact, the failure is on the part of the guy who didn’t get the joke.
The Hamlet Project 