Besides, a good Barry Allen needs a sense of humor to counterbalance some of the darker DC characters like Ben Affleck’s Batman or (in this universe) Henry Cavill’s Superman, and it looks like Miller is bringing that to the equation.
Ezra Miller eventually made a point to note that the assembly of his Justice League Flash suit became easier as production on the film progressed, but those first few fittings were some of the most challenging.
We all need to find ways to keep ourselves occupied during boring and tedious periods of work, so I guess pretending to be a woman from the Victorian-era waiting for suitors is one way to pull that off.