This morning I found 2 big fat slugs like cork screws around each
other doing the nasties. They were hanging from a twig.

How many can say they've seen slugs mating? I've seen small pets
including fish, different insects and flies, but this is pretty
rare.

I've heard that porcupines do it standing on their front legs so they
don't stick each other. Rabbits are really funny to watch because
after doing it the buck falls off and screems in joy. At least I
assume he's not screeming in pain.