No joking, being serious here
If you have a two piece toilet, especially one a few years old, check the seals on the bolts securing the tank to the toilet. If they look funky replace them!
Costs about $20 dollars and is so easy even I can do it.
Why?
A coworker of mine just had one of the seals on one of the bolts fail. This caused the water to drain out of the tank. But it was not just the 4-5 gallons in the tank, the lowering of the water level triggered the tank flowing mechanism and it ran for hours. She had a hundred gallons of water if not more all over her house when she got home last night.
The seal must have failed that morning.
This is a case of where an ounce of prevention can avoid hundreds/thousands of dollars in damage. It happened in her upstairs bathroom so she has floor/ceiling damage.
Check those seals! They do not fail safe!