The few documented cases of animal humor are physical in nature. The researcher Roger Fouts reported in 1997 that Washoe, a chimpanzee he had taught to sign, once urinated on him while riding on his shoulders, then signed 'Funny' -- touching its nose -- and snorted.
[Zoo officials in Kirby, Misperton, England, often had to compensate visitors for eyeglasses stolen by their monkeys. An investigation soon revealed the problem: The monkeys were snatching glasses when visitors leaned in to read a warning sign: "Beware! These monkeys steal spectacles."]