He's not stupid; he's possessed by a retarded ghost.
Mysteriously, the soul-mate of a man named Paraic will more often than not be called Kate. This is a phenomenon which has baffled many for centuries.
Some say that if you stand close enough to him, you can hear the ocean. However, this is debatable. Unlike the part about Kate. Which is definitely true.
Doug: Really, what was his name?
Kate: Well obviously Paraic!