doppledangler
An apparition or double of a living person's dick. Although very difficult to prove empirically, every person's dick has an exact twin belonging to another person. Sometimes dopple dangler.
In the gym showers, Curtis had the great misfortune of coming across his exact doppledangler. The sight of the doppledangler--his own dong that he knew so well--in between another man's thighs made Curtis feel very comfortable.