Octopuses can mate without leaving the house. Because the male’s sex organ is at the end of his arm, he can set up his den next to a female’s, stretch his sex arm all the way to her house, and get the job done from afar whenever he feels like it. Scientists call it the ‘distance position,’ and it also allows smaller males to mate with a larger male’s girlfriend because they can move in close to give her the reach-around when he isn’t looking. Source Source 2