The thing that causes my nads' to retreat into my body cavity up to my diaphram is putting my hands into something that's wiggling/crawling on it's own...like if you're climbing up the side of a hill and you reach up and grab the edge and you've got that "squishy feeling" between and on your fingers and it can be anything from pigeon crap to spiders?
I HATE THAT!!!
(ok...i feel better now...)