Shooting three (or more) arrows at once...
So how well does this stunt work?
Shooting three arrows at once is fun. Pointless, but fun. You just have to accept that they are going to end up about 4-6 inches away from each other. If you do it right they will be in a nice line at the same angle you held the bow (assuming your arrows are all balanced and of equal weight). The distance between them is determined by the distance to the target and the angles of the arrows relative to each other on the bow. A 1/8" change at the bow results in a change of at least an inch at the target.
Also, and much more importantly, the amount of energy imparted by the bow is finite; shooting three arrows at once means that each arrow only gets a third of the energy a single shot would have. So if a single arrow goes 90 meters (Olympic distance), three arrows will only travel 30 meters each. They will hit with only 1/3 the impact. It's a supremely ineffective technique for anything other than extremely close distances.
I really wish somebody would use that as a plot point just once.