A question often raised to prove that Mafia is unrealistic and "Just a Game" is "Why would anybody not recognize Celebrity X?" Basically the story goes that if this were really happening, the people of a town would all recognize each-other by face and a Mass Roleclaim would be unavoidable. What the question fails to account for is that the relationships between human beings are much more complicated than the relationship between Mafia Roles and that this complexity accounts entirely for the suspicion and uncertainty. You may know what somebody's job is (like a local doctor), but do you know what he wants? Do you know who he works for? Those questions can't be so easily answered.
This presents a problem for Game Moderators writing Theme Games, as the players all know the motives of the characters, so long as they know the source material. If the players are to play the game as players and not dispassionate observers, they must be unsure of the outcome of the story. There are many approaches to this problem. One is to change the motives of characters. Another is to use sufficiently ambivalent characters so that motives cannot be ascertained by knowledge of the source material. It is the contention of some that Theme Games should rarely (if ever) be written with the source material open to the players.
One other possible solution is to use a source material where alignments are known to shift rapidly or where there are villains that can potentially replace relevant characters from the material without being noticed by appearance (shape-shifters, mind control, ect). Making powers based on equipment allows you to also assign powers regardless of in-universe abilities. In such a situation, the appearance and names of the characters could be completely open. Alternatively, you could pick a source material where everyone could be constantly disguised.
It is, of course, simply possible to disregard canon allegiances when designing your game.
See also the Innocent Child role, where everyone actually DOES know that the role is innocent.