A joke cycle is a collection of jokes about a single target or situation which displays consistent narrative structure and type of humour. Some well-known cycles are elephant jokes using nonsense humour, dead baby jokes incorporating black humour and light bulb jokes, which describe all kinds of operational stupidity. Joke cycles can centre on ethnic groups, professions (viola jokes), catastrophes, settings (…walks into a bar), absurd characters (wind-up dolls), or logical mechanisms which generate the humour (knock-knock jokes). A joke can be reused in different joke cycles; an example of this is the same Head &amp; Shoulders joke refitted to the tragedies of Vic Morrow, Admiral Mountbatten and the crew of the Challenger space shuttle. These cycles seem to appear spontaneously, spread rapidly across countries and borders only to dissipate after some time. Folklorists and others have studied individual joke cycles in an attempt to understand their function and significance within the culture.