Crapon

Crapon is a phenomenon that happens to some males whilst taking a dump. It's reported that some guys get so turned on by the feeling of dropping logs into the toilet they get a hard on. In some circumstances they actually shoot a small amount of jizz.

Andy: Hey Gaz, Greg, I've just been to the toilet and dropped my load, it felt so good I got a boner and shot my load. It's called a Crapon.
Happened to you guys before?
Gaz: nope
Greg: nope