It's called Paradoxical Hotness.
You have several specialized nerve endings. The neurons that sense temperature are just beneath the skin. You have one type that senses warmth and another that fires when it senses cold. Oddly, we don't have receptors for hotness. That's where the fun comes in. I mean, if you ever get bored enough. Or if you have a little brother you want to bully.
The way hotness works is BOTH the warm and cold sensors fire. ("Fire" means they send a message to the brain. The brain accepts messages from nerves as true.) For example, if you jam your hand into, say, a bacon slicing machine or an electric toaster, pain neurons fire. The brain believes you and tells your vocal chords to start screaming. Or wherever screaming comes from. The point is, the brain believes the messages the nerves sent it. And that is a good thing, by the way.
But there are no specialized neurons dedicated to feeling hotness. Fancy that. And God's little attempt at nerve economy can be the source of entertainment, if you like. Here's how:
First, let me remind you (since it has been two or three paragraphs ago since I mentioned it) that the body senses hotness because something hot triggers BOTH nerve receptors - warm and cold. If you hold your hand under very hot water, you will jerk it away quickly because the hot water has triggered both the warm and cold nerve cells near the surface of the skin. Are you with me?
Do this experiment. Run two small copper tubes side by side. Have cold water running through one tube and warm water (not hot water) running through the other tube. Now simply reach out and grasp both tubes in your hand. Simple, right? Har!
Even though your logic tells you it isn't hot (because it isn't really hot) you still can't hold onto the tubes. You simply must let go because you feel searing hotness. This is such a marvelous discovery. Or at least it is to little boys.
So, what you do is, you get a victim (or you try it on yourself because you know your superior reasoning skills will prevail over your brain's reflexive reactions) and you let the person feel the pleasantly warm water coming out of one tube; then you prove the other water is cold. Neither is hot.
If you ARE able clench your fist around them both for more than a second or two, I guarantee you will feel the pain of extreme hotness. But DO try it sometime.
Perhaps you have discovered other ways to amuse yourself with your body. If so, please share.