Justice League: Mortal - What Really Happened?

2. What Went Wrong?

Unfortunately, by the time The Dark Knight came around, Warner Bros. decided there was little sense in pursuing Miller's Justice League, which had suffered from countless delays by that point and seemingly threatened to step on the toes of Christopher Nolan's Batman trilogy.

At the time, and even today, to an extent, Warner Bros. have always been worried about the idea of there being multiple versions of DC's characters on the big or small screens at once. A planned Bruce Wayne origin series was shelved in the run up to Batman Begins' release due to fears that audiences would get confused by the idea of there being two Bat-men, and though Smallville managed to survive Superman Returns, it likely only managed to do so due to its following, as well as the fact it had already been running for five years by the time that film had released.

Point being, although Mortal had a lot of traction for a period of time, its eventual cancellation wasn't as surprising as it probably should've been. WB have never been keen on the idea of multiple incarnations of a character appearing on the screen at once, which is why - even today - Gotham isn't allowed to explicitly reference Joker or Harley Quinn.

Apart from that, Mortal's delayed production eventually meant that its budget had ballooned to an estimated $300 million, something Warner Bros. weren't exactly keen to indulge after Superman Returns tanked just two years earlier.