Well, you got a good response from the others, so at least you aren't going to be isolated with people giving you hate-filled stares for making jokes about disability.
My boss makes fun of himself. "Got a touch of the Parkinson's this morning," he'll say, as he struggles to control his shaking hands as he gives me a piece of paper with the service call info on it.
Make jokes about your boss having downes syndrome in front of him. No matter how perfectly timed it is.