This movie would have been good if Evan was in it.
Despite the film supposedly taking place in 1942, there are nearly constant anachronisms: characters use cell phones, drive modern cars, use modern-day slang ("pleb", "bell-end"), and refer to people who had not been born yet (notably Bob Ross, who serves as a major plot point in the film despite being born several years after the film takes place. These are all, however, completely intentional, intended to be self-referential jokes in the style of Mel Brooks.
When the paper plane thrown by Detective Johnson hits Lewis, the hand that threw the hand can be seen on the side of the frame for about three frames.
Throughout the film, a tripod can be seen in the background of shots, most notably during Detective Carter's introduction and during the argument he has with Cluz in the parking garage.
When Lewis enters the office to find Henderson in Act Three, the reflection of the cameraman can be seen almost center frame as the camera pans over to him.
Several actors wear their fedoras backwards for some scenes. Ari Froehlich and Blake Weise were repeat offenders.
Johnny B. Oy's Irish accent changes from a leprechaun-like Limerick accent to a more realistic Belfast accent in the very next scene.
In the scene where Chief Houston congratulates Lewis on his work, he drunkenly calls Lewis "Cluz". This was originally a mistake, as Blake Weise, who portrays Houston, mistakenly called Joey Cianfrani "Langley". Nick Geoghegan liked the idea of a drunk Houston praising Lewis as he once did Cluz, so the line was re-shot with Cluz's name.
Just before the transition from Cluz's office to the meeting with the informant, Lewis and Henderson can be seen walking by the door. Lewis holds a cigarette, despite later claiming that he doesn't smoke after offered a cigarette by Henderson in the second act.