More than likely this change in tone came when Joss Whedon came into picture, as he’s been shepherding Justice League to completion.
And if the previous trailers are any indication, Bats and Jason Momoa’s Aquaman are going to be quite the unlikely team.
Ben Affleck’s comment to Geek Magazine (via ScreenRant) is setting up Justice League as an exercise in the audience getting familiar with the various personalities of its members, just as Batman has to play with others that have various abilities and quirks.
Naturally, the guy who made The Avengers a fun ensemble film in 2012 is going to leave a mark on this big ticket superhero collaboration.