Penis To Spare
The little earwig (Euborellia plebeja) has an extra penis. Not only that, they both work. Until recently scientists figured the second penis was not a fully functioning one because it points the wrong way. Japanese researchers Yoshitaka Kamimura and Yoh Matsuo of Tokyo Metropolitan University interrupted a couple of earwigs while they were getting busy, causing the male to disengage and leave his penis behind in the female. Later he was found mating again, using his "back-up" cock. Handy, no?
More interesting however is that paired penises are not completely uncommon, which many accounts of the earwig discovery left out. They are found among snakes, lizards, and crustaceans. Some scientists suggest that they may have originally evolved in pairs like legs and other external body parts.