Comic fans are very particular about the adaptation of their beloved heroes, so both the actors and studio have to do a fair amount of research to properly honor the source material.
As such, they’re both affected to do a fair amount of research, including actor J.K. Simmons.
Simmons is currently playing Commissioner Gordon in the DC Extended Universe, and recently revealed what he did to prepare for the daunting role last made famous by Gary Oldman.
As such, plenty of A-list stars are signing on to play characters from both Marvel and DC comics, which is a job that comes with lots of pressure.