Infinite monkey theorem

According to K9 Mark II, the infinite monkey theorum of statistical mechanics postulated that an infinite number of monkeys with an infinite number of pencils might eventually come up with the complete works of William Shakespeare. The Fourth Doctor said he would prefer if they produced the works of P. G. Wodehouse. (AUDIO: The Eternal Battle)

Behind the scenes
Though the Doctor brings up the infinite pencils in the context of his defence of the tools' importance, the infinite monkey theorum traditionally concerns an infinite number of typewriters for the monkeys in question.