What is the funniest thing you have ever said in the spur of the moment?

Oh man, I still cringe when I think about this one. A few years back, I was at a hardware store picking up some supplies and I ran into this guy I hadn't seen since my teen years. I was pretty distracted looking for some specific screws, and when he tapped me on the shoulder, I just blurted out "I'm not the father!" without even looking at who it was. I don't even know why, I think I was watching some reality show the night before and my brain just glitched.

The look on his face was pure confusion, and honestly, I just wanted the ground to swallow me whole right then and there. I had to scramble to explain that I was just being a total idiot, but the damage was done. We had a good laugh about it once he realized I was just being a complete moron, but man, talk about a spur of the moment brain-fart that makes zero sense.