Sleeping Wrong?

I didn't wake up with a stiff neck,it came on for no discernible reason some time around an hour after I got up. But that isn't really what I want to talk about. The phrase sleeping wrong is what's on my mind,is it just me or is that one of the goofier sayings to come along? Seriously,how exactly is the "wrong" way to sleep? "Oh,you see I fell asleep standing on my head and upon waking discovered that was the wrong way to sleep." Other than maybe someone suffering from narcolepsy,I don't see that scenario happening on a regular basis. So how else could a person sleep wrong? I suppose those of you that have no problem falling asleep might nod off in a chair with your head at a bad angle,but why does that make a person get a stiff neck? If you observe animals sleeping you will get my point,I have seen them jump up,give themselves a shake and be ready to go after sleeping in positions that would seemingly cripple any being. I have to be pretty comfortable to fall asleep and stay asleep so maybe I am missing the whole idea behind "sleeping wrong". One of the only circumstances that would completely qualify as sleeping wrong would be to fall asleep with your head submerged in liquid...now that would be sleeping wrong!