How can parallel universes be proved to exist if they are unobservable?

[khanster]

It seems highly unlikely that other copies of "us" exist in an inflationary multiverse scenario.

The fluctuations that give rise to different universes would evolve differently would they not?

The infinite monkey theorem seems to agree concerning the improbability of a monkey typing out Hamlet in a finite amount of time...

http://en.wikipedia.org/wiki/Infinite_monkey_theorem#Probabilities

Even if the observable universe were filled with monkeys typing from now until the heat death of the universe, their total probability to produce a single instance of Hamlet would still be less than one in 10^183,800