Houses and cars kept open
This is something that maybe happened some time ago, when the tourism was not so big. Now, most of the people if not all of them are keeping the cars and the houses closed. There were also some incidents not very long ago that made the locals pay more attention to this things.
Men being paid for marring Icelandic women
Actually, this was constantly on social media and in the news. Nobody is paying men to marry their women. In the Icelandic culture, people do not get married very young. They have children and the family itself but nowadays the couples leave this event for later in their lives as it is not a big priority.
Elves and trolls
The elves and the trolls of Iceland became pretty famous few years ago, as authorities tried to protect some areas 'designated to elves'. They acually consider the elves and the trolls the power of nature, which we should never forget about and try to consider everytime we spend time in the nature.