That reminds of a story about an Indian couple travelling Europe. SO, obviously, within the Schengen countries you do not need additional visas, something foreign to said couple. So, they crossed Eu border by train and ended up in another country. Confused over what to do next, they talked to the next police officer they found, because the couple was sure they couldn't just continue their journey without any further control. Explanations didn't work, so the easy solution was to use an official looking, but totally irrelevant, stamp to put on the back of their train tickets (in order to not cause confusion with the tickets or official passports). Source: I know the police officer in question.