* TheDanza: Probably the only occasion in recent history where this happened with an actor playing someone who really existed: '''Johnny''' Depp as '''John''' Dillinger. And the real Dillinger often was called "Johnnie". They coincidentally share initials.
* FontAnachronism: As John Dillinger and his associates leave the red train car, the car number seen on the outside of the car is in the Helvetica font, which was not created until 1957. The film takes place in 1933, a couple decades too early for Helvetica.
* RetroactiveRecognition: Creator/ChanningTatum , than only mostly known as that guy from ''StepUp'', pops up very briefly as Pretty Boy Floyd before being shot and killed by Melvin Purvis.
** CareyMulligan pops up very briefly as one of Anna Sage's girls. It's a role that goes by so quickly you could easily blink and miss it.
* TechnologyMarchesOn: Watch this film, then try to imagine how things would turn out if the police had radios, cell phones, radar, helicopters, K9 dogs, etc.
** For the time period of the film, this was also present. Bank robbers were able to gain access to submachine guns and cars with reliable V8 engines more easily than any police department, so you could easily drive away while the sheriff was still crank-starting his old vehicle. Essentially, if a robber got away without being shot, there was little chance he would be caught.
* WhatCouldHaveBeen: Bryan Burrough originally started writing ''Public Enemies'' as a script for a TV miniseries, but didn't feel comfortable writing fiction and retooled it into a nonfiction book. Making it, almost, a RecursiveAdaptation when adapted to film.