Apparently Viggo Mortensen became quite fond of viciously and violently head-butting his co-stars, to the point where he almost knocked Monaghan out.
During a recent Reddit AMA session, Dominic Monaghan addressed a particular fan question regarding fun on-set pranks conducted by his fellow Lord of the Rings stars.
Aragorn may have used a giant sword as his trademark weapon during the Lord of the Rings trilogy, but Viggo Mortensen could probably handle himself in a fight using nothing more than his cranium.
I think he might be confusing the terms “prank” and “assault,” but that’s none of my business.