Zack Snyder talks an awful lot about the universe building he did for Justice League. The director began working on the DC film from the start, but unfortunately had to step down after a family tragedy occurred, and Joss Whedon was hired to finish the job. Whedon apparently changed a decent amount of the film, leaving fans desperate for a "Snyder cut."
The director had plenty of plans to introduce characters to the DC Extended Universe with Justice League, which he successfully did with the likes of Deathstroke and Mera. However, Snyder revealed there was another hero he was going to include. Ryan Choi, a.k.a. The Atom, was also supposed to featured in the movie.
Earlier this year, attentive fans noticed when re-watching Justice League that Choi's name was displayed on the side of a computer screen, revealing that in the DCEU, the superhero is an employee at S.T.A.R. Labs.
A fan also found a Justice League promotional picture featuring Silas next to another scientist, who Snyder has confirmed was indeed Choi. The scene, however, was ultimately cut during post-production/reshoots.
Outside of the comics, The Atom has most prominently appeared in Batman: The Brave and the Bold. Choi's appearance in Justice League would have likely been minor, which is understandable. Still, including him as a S.T.A.R. Labs employee was a wise choice by Snyder, because he would have retained his scientific background.
DC's next movie to hit theaters will be Aquaman directed by James Wan, set to premiere on Dec. 21.