Are there examples of humor and irreverence in Buddhist scriptures?

Irreverent humour is reasonably well-tolerated in some sections of modern society. For instance, jokes about the pope and about pastors' wives are fairly widespread among even church-going Christians. There are also plenty of God and Devil jokes. What, if any, role does humour play in Buddhism? Are jokes about The Buddha, or Buddhist gurus and their disciples taboo or in bad taste? If so, what is the basis for this? Is humour discouraged for reasons such as, say, retarding progress towards Nirvana? Are such jokes considered against Vinaya?