I'm speaking, of course, of toilet paper breakthrough. You finish your movement with what you think is a clean break. You're back there cleaning things up. Shouldn't be too much, after all, you felt it plop in. By the time you realize it's a little more liquidy than you thought, it's too late. First your dominant cleaning finger rips through. The momentum pulls a couple more into the abyss. You instantly pull your hand away but it's too late.
You give your hand a good look, maybe sniff it a couple of times to be sure then look up toward the sky and scream "Why Me!" at the top of your lungs. You have to be careful if you're the type that uses his or her hands for emphasis when talking.
You successfully avoided changing your kid's diaper the whole 10 years he was wearing them for this exact reason. But Karma got you tonight. After you clean up, you keep sniffing your fingers. Is it your imagination or is there still some odorous evidence? What are you going to do if someone tries to give you a sandwich to eat? What if your wife says something while you are laying in bed tonight?