Only in Korea will you see a message that reads, "Don't throw toilet paper in the toilet." Because... why be logical, right? Toilet paper doesn't belong in the toilet, dumbass!
Depending on where you go in Korea, you might see signs telling you to throw your used toilet paper into the toilet because the paper will "melt" in there (as I saw in a Korea University restroom: "화장실 휴지가 물에 녹으니 변기에 버려 주십시오"), but you're more likely to see signs like the above. So you may be asking yourself: where do you throw the used toilet paper, then, if you can't throw it into the toilet? The answer: you throw it into the wastebasket right next to the toilet. This is one of the most disgusting things a person can do, in my opinion: a trash can full of shit-covered toilet paper is about as filthy as a leper's asshole. But many Koreans fear that, if too much paper enters the plumbing, a huge and disastrous backup will destroy civilization as we know it. The only way to keep the Earth from exploding is to throw the used toilet paper into the wastebasket. Ayup.
I ignore all such signs, of course.