Although the penis is not really a bone - it only feels that way 90% of the time! - it can still be broken, if enough force is applied at the correct angle (e.g. falling on it, or slamming it in a door).
Often, there is an audible "cracking" sound accompanying this tortuous, apocalyptic event. And, like a broken bone, the fractured penis needs to be "set" as soon as possible after breakage occurs, to ensure proper healing.
A broken penis is a medical emergency, so if you are experiencing the symptoms of bucklecock (screaming in pain, penis misshapen and pointing off at a sickening angle, significant other has feinted from the sight of it, etc.) then I implore you to stop reading this and seek professional medical assistance immediately.