9. Batman Discovers The Watchmen
Given Watchmen is an entirely separate franchise to the larger DC universe, it seemed impossible that the two would ever cross paths - made twice as impossible as a result of Alan Moore's unbridled rage at any potential suggestion of his creation being used in any other form that its original comic.
But this rage didn't stop the Watchmen film being made, and it did nothing to stop the DC/Watchmen crossover Doomsday Clock. Despite fans reacting to the comic as though it were literary Marmite - either adoring it or despising it - it's hard to argue with the idea that the introduction to this whole topic is golden, with the panel of Batman holding the Comedian pin being one of the most iconic moments in DC's recent history.
It's off the wall, it's completely out of nowhere, and it's a million percent sure to piss Moore off - and you can't help but love it just a little for all that.