Some people will just stick their cocks in anything, if they're horny enough. I remember one rl medical show years ago (though I think they did something similar on a fictional one also) where a guy got his stuck in some sort of long metal pipe. They had to cut the pipe...and be very careful not to cut him....to free him, because he couldn't lose the erection to get loose.
(The book I read where the guy stuck his in an exhaust pipe was a minor plot point, fortunately, And totally unexpected.)