I had been sleeping on my arm once and it was completely numb, I mean COMPLETELY numb, no feeling at all. I was laying on my back with my arm somehow underneath my back. I was slowly waking up when it spasm-ed or something, and flew out from under me and landed on top of my chest. I was instantly woken up with this heavy arm just draping itself over me, and I'm thinking to myself, "What? How did that get there?" So I tried to move it, but couldn't, it felt like my arm was still down by my side... I'm like, "Who's arm is that?!?" and I let out a very "WHAT THE FUCK?!"