I read this somewhere, but can no longer find the article. The theory was that when the heart is on the left side of the chest, blood pumps from that side, causing the hanging appendage to lean slightly to one side. (I forget whether the same or the opposite side.) So, a penis that hangs to the opposite side from what is "normal" is supposed to be a sign of dextrocardia (having one's heart on the right instead of the left side).
I just wondered if this theory was true. Please cite sources in your answer. Thanks!