Also, a second point. If one had infinite monkeys then they could conceivably do any task in precisely zero time. This is why the Shakespeare bit usually refers to a finite number of monkeys but an infinite span of time. The logic of such a thing is simple.
One has roughly a 1:128 chance of randomly selecting the first character of Shakespeare's first play. As one adds additional characters, the odds increase. Assuming there are n characters across the works of Shakespeare, the odds of randomly selecting characters (as if one were a monkey) that just happened to be a retelling of the works of the Immortal Bard are n^128. You'll find that this results in a very large number, but any number, no matter how large, is irrelevant in the face of infinity.