Last time i mounted a wall clock (at home), i did it upside down. . . "With time" the family learned to read it, and when we had the walls painted after a year and I mounted the clock the "normal way", no one could decode it right away for several weeks.
Reminds me of the psychological experiment with the prism googles, . . . and the ethological observation of the rat that jumped the bar in the labyrint, long time after the bar was removed.