Public toilets were famously popular in Roman Empire. Romans were also fond of graffiti. The fact that people scribble stuff on bathroom walls is thus a historical inevitability. Romans, Mayans, Vikings and Varangians all left their names or funny sayings wherever they went. Hagia Sophia still bears the name of Halvdan, who carved it while in the employ of the Byzantine emperor.
It's only natural that bathroom goers would do the same.
Do you have any funny pictures of bathroom stall advice? Post them below, or vote on your favorite!