A Spring Got Stuck Up His ___

(This is a fictional poem) I've had the same mattress for over twenty-five years. When my teenage son was having sex on it, a spring went up his rear. It went up his ___ and it got stuck. I caught him in my bed and he was out of luck. I was very mad and I started to shout. A proctologist had to come over to get the spring out. I knew he had been having sex because he was wearing a rubber. I tanned his hide and you should've seen him blubber. He thought he'd get away with it but he did not. If I hadn't been too cheap to buy a new mattress, he wouldn't have got caught.