http://www.sexualrecords.com/WSRphysiology.html

Those who have more than one penis have a condition called diphallasparatus (yes, there are medical names for everything). An extremely rare disorder (fewer than 80 cases have been reported), it has nonetheless been exhaustively investigated by the medically bent. The results of such studies can be summed by the following snappy observations:

1. Those in possession of a diphallus tend to be sterile, due to either congenital defects or difficulties in application.
   
   
2. Urine may be passed by both penises, by only one, or, incredibly, through some other aperture in the perineum.
   
   
3. All manner of duplications have been met, ranging from organs that fissure into two to the presence of two distinct penises positioned at some distance from each other.
   
   
4. Most diphalluses lay side by side and are of equal size, but they can be seated atop one another, with one distinctly larger than the other.

Double the meat doesn’t necessarily mean double the fun. Most sufferers are unable to perform sexually, which must be one of the all-time bummers. Still, for those able to function it certainly lends itself to some interesting diversity of technique.