It was on Gray's Anatomy a couple of years ago, and the day after people were searching the net to find out if it's a real thing.  It is.  A web page that popped up on the Scientific American website after the episode explains it:

"It's what we call penile fracture. It is a severe form of bending injury to the erect penis that occurs when a membrane called the tunica albuginea tears. The tunica albuginea surrounds the corpora cavernosa, specialized spongy tissue in the core of the penis that fills up with blood during an erection. When the tunica albuginea tears, the blood that is normally confined to this space leaks out into other tissues. You get bruising and swelling.

How exactly does penile fracture happen?
Any situation during intercourse when there is thrusting and when the penis, instead of penetrating its normal location, is hitting some solid structure (such as the perineum).  Usually this occurs during regular vaginal sex with the woman on top, but it can happen in the missionary position or during sexual acrobatics. We had this patient who suffered penile fracture after running across the room and trying to penetrate his wife with a flying leap."

Another site says that blood can shoot out the hole, or if the skin ruptures, can come out there too.  Either way, it's a frightening experience for those involved.

The flying leap sounds interesting though.

Re: Aurora Snow talks about the broken penis....

I think Prince Yahshua is dealing w/this right now.