When the toilet is clogged and you plunge it down using your foot.
The origin of Shitfoot is when
Aria Nafeces brought his
shit stained shoe into class and smeared satanic rituals/ naruto jutsus all over the floor. He was soon taken out of the class to wash his shoe in the bathroom, which took copious amounts of times, and the poor chair was taken to maintenance.
Since the fateful shitfoot day of September 4th 2018, it is said that if you plunge your
shit clogged toilet three times and say "Shitfoot No Jutsu", you
will summon Shitfoot himself to your bathroom. He
will then smear shit all over you.