Ewing played center for the Georgetown Hoyas for four years and was named as the 16th greatest college player of all time by ESPN. He won Olympic gold medals as a member of the 1984 and 1992 United States men's Olympic basketball teams.
Sleep paralysis is a temporary inability to move or speak that occurs when you're waking up or falling asleep. It's not harmful and should pass in a few seconds or minutes, but can be very frightening.
REM sleep is an active mind inside a paralyzed body, while nREM sleep is a resting mind inside a functioning body. This is why sleepwalking is possible during nREM sleep and not during REM sleep: your body is paralyzed during REM sleep but not in nREM. As for why sleepwalking occurs... well, we still don't really know. See Wikipedia: Sleepwalking for much of the current knowledge.