Did you hear about this one: Your dad constantly tell bad jokes in socially inappropriate situations. That's just dads being dads ... or is it? Maybe he's suffering from the Joking Disease.
No, it's not a joke: though rare, the Joking Disease or witzelsucht (derived from the German word witzeln meaning to joke and sucht meaning addiction) is quite real. The neurological disease is caused by damage to the frontal lobe of the brain. People with witzelsucht compulsively tell jokes and puns, but do not seem to "get" the humor - they don't laugh or smile, nor do they show any emotional reaction to jokes, either their own or other people's.