Large-scale moviemaking is a messy business. There are so many people's livelihoods at stake, so many competing visions and - crucially - so much money on the table that there's little chance of things running smoothly. Getting a blockbuster made seems like trying to control the weather: giant, unforeseeable forces are at work, making human decisions more or less irrelevant.
There are perhaps no blockbusters bigger at the moment than superhero franchises: six of the top twenty highest-grossing films of all time are Marvel movies made within the last decade. So it's not surprising that these films have especially chequered production histories, crisscrossed with the rising and falling fortunes of various directors, tossed on the capricious tides of the studio system.
As such, some well-known superhero films have suffered from tempestuous behind-the-scenes politics that led directors to leave their projects, even if they had spent years working on them. These would-be movies offer a glimpse into another universe, let's call it Earth 212, in which the world was granted a very different batch of superhero films, at the hands of a very different group of directors.