YSK: Throwing firecrackers into a toilet doesn't just make a funny splash, it will usually shatter the bowl and ruin the toilet beyond repair. If it goes into the plumbing the damage can be even more severe and very costly.

Why YSK: People often see this 'prank' on TV or in movies and then decide to try it out. They are usually very surprised when they end up actually destroying the toilet. This is something you should know ahead of time so that you can be the voice of reason when hanging out with friends and one of them suggests throwing a firecracker into a toilet. It can really ruin your night.