as far as i can recall that guy hitting his head COULDNOT see a thing through his helmet. The bumping went unnoticed until it was picked up by cinema viewers.
Hmm anyone say "Shoot the continuity people" :>
also I recall hearing once when i was a wee lad that the guy who smacked his head did it intentionally after being dared by a friend.
Dont know which story is true but still it's funny as hell & cinema history & IMO ABSOLUTELY NOTHING WHATSOEVER to do with the "creative genius" of GL