It's a widely held belief that water falls down the drain turning in the same direction in one hemisphere of the Earth and the opposite direction in the other hemisphere.
I remember, an X-Files episode (which implies that this happened about 15 years ago) where Mulder saw the water falling down the drain turning clockwise and that, Scully, is impossible because we are in the northern hemisphere and water always turns counterclockwise here.
It's also quite famous that episode of The Simpsons in which Bart rides a mess with Australia on account of the water spinning in different directions depending on the hemisphere you are on. It is a premise that is repeated several times on the episode giving it as true, to the regret of those who are hardcore fans of this show and feel sorry about its continued lurching between episodes that defend critical thinking, positivism and rationalism in contrast to other episodes that do just the opposite defending pseudoscience, postmodernism and magical thinking. Fortunately, it seems that the times of magic in The Simpsons are left in the past (excepting those pleasant Halloween specials) and ultimately the rational option is gaining ground. Or maybe it's just what I want to think.
Actually, Bart's attitude during the chapter is quite strict from a scientific point of view, the problem is with the facts observed during Bart's experiments. Lisa transfers to Bart her beliefs about drains. But Bart, instead of accepting it without doubts, adopts a skeptical attitude and is willing to test it and try to nullify it. Since he doesn't find a counterexample in a first trial, he provisionally accepts the hypothesis but goes on doing more experiments in search of a counterexample. And so it ends up causing the conflict with Australia.
During the chapter, Bart confirms in each trial that water turns in the direction predicted by the hypothesis, but would it be the same in the Real World ™ instead of a cartoon world? How many of those who have heard this belief have acted the same way? How many have tested the transmitted hypothesis? Anyway, recently, the same day, two separate and distinct people said quite convinced to me the plausibility of this hypothesis, but I could not just accept it. I could not deny it either without a counterexample. I had to test the hypothesis, do the experiment and then say what I have to say about it with some basis. And this is the result: