I can never remember jokes, and just rely on my wits to be wildly amusing.
However, the only two jokes I can recall off the top of my head are ones I could tell my mother. One involves a pram, and the other relates to the earthquake in Pakistan. If you were being analytical about them, one would be seen as a joke about child abuse, and the other would be racist. Both totally unfunny subjects, yet both jokes raised a groaned chuckle when told to me.
Funny old world.