The Auto Octopus is the act of one male individual ripping off his own penis and then shoving it so high up his rectum that it seemingly disappears. The individual has to then defecate in order to retrieve his penis. This practise is a method in which men are fully able to 'fuck themselves' however, it is known to be extremely painful.
The origin of the Auto Octopus comes from the rather unusual mating strategies exhibited by the marine creature: the octopus. In order to mate, octopuses must rip off their penises and then throw them at the females they are wanting to reproduce with.
Man 1: "Shit dude, last night I finally manned up and performed the Auto Octopus"
Man 2: "Far out bro, that is hard core!!"