Corrected entry: Vermin tells his sidekick that he plans to kill Tommy Kelly at the exact moment that Cagney is killed in the movie. But there's no way for him to have known anything about what happened in the movie, because no one had even seen it yet. Even though the specific movie is never named, the radio announcement Vermin had listened to the previous day clearly states that DA Kelly and the governer would be attending the premiere of Cagney's new movie.
Corrected entry: In one of the scenes at Johnny's pet shop, a shot out the window shows a passerby on the sidewalk answering a cellular telephone. The movie takes place in the 1940's.
Correction: There is no scene like this that occurs. Even if it was possible something like this happened on a different version, you need to be more specific about which scene and version (and possible provide a screenshot), because I couldn't see anything remotely close. Additionally it should be pointed out the pet shop scene is set in 1935 (not the 40's) and the movie came out in 1984. The first commercially produced handheld cell phone came out in 1983, cost $4,000, weighed almost 2 pounds, and was 13 inches tall. Highly unlikely that an extra happened to be accidentally caught on camera answering his cellular phone.
Correction: First, there's no evidence the movie was never seen by anyone. It was merely premiere night. Vermin was already disguised as a theater worker before telling the sidekick his plan, so it's plausible he did at least see part of it to plan his attack.
Bishop73