Producing things like maps, dictionaries, encyclopedias and the like take a lot of work if you do everything from scratch. Of course, you could cheat and just build off of someone else’s work, or simply copy them outright. To protect against this, some creators insert what is known as fictitious entries into their work, to act as literal copyright traps. In map making this process is often known as adding in Paper Towns.
Wendover Productions put together this great little video explaining this idea in a bit more detail:
It’s clever, I’ll give them that, but in the same breathe also a little annoying, particularly when you need to trust a map in getting somewhere – i.e. when you are desperately counting on that petrol station being there when you arrive!