Topic. I've been wondering about this for the past few days. Many of the guards in the MGS series are capable of standing up while sleeping. I'll be posting this on the other MGS boards as well. --- Everybody wants to go to heaven but nobody wants to die.
I think you have to see it more like dozing off. But people can technically sleep while standing up, just think of sleepwalking. I think it's even possible to take a nap with your eyes open. --- Straight to the pointless.