Or is it? While “Birdman” exists in its own meticulously realized world, it’s very much of this time and place from a pop-culture perspective, with references to other real-life actors like Robert Downey Jr. and Michael Fassbender who’ve enjoyed enormous success when they’ve donned the superhero duds. The script from Inarritu, Nicolas Giacobone, Alexander Dinelaris and Armando Bo is cleverly meta without being too cutesy and self-satisfied.