Reddit user Ruinthefun, though, looked into the game code and said that they think the interaction for creating a fire in your toilet with piss was built into the code intentionally. Most people are assuming this is just another wacky Sims 4 bug, like when babies used to get stuck in a void right at the very edge of a lot, lost forever to geometry.
They now have a really, really good reason not to miss the bowl. No longer would you have to worry about your male roommates leaving the toilet seat up. Imagine how powerful that would feel, ejecting piss-flames from your body. Imagine, taking a piss and instead of a sad tinkle you hear a crackle of flame as your pee stream hits the water. As you can see in this beautiful Reddit video, it's even more incredible in motion.