There are two guys at work that look nothing like each other but get their names mixed up all the time.  I have worked with them for a few years.  But because they are Asian, someone accidentally called them by the opposite name, and it became a running joke ever since then.  But ever since then, the accidental switching of their names has increased.  Even I have to stop and think about it for a second, and I never had that problem until they started joking about it.  Psychology is a really weird thing.