The actor - who starred alongside Elijah in 'Lord Of The Rings' - often plays practical jokes on set to keep his colleagues in a good mood and once played a prank which lasted for weeks.
He said: "There's no sense in doing something, especially if it's a hard job, if you can't have a little fun.
"One time, I called Elijah Wood every day for six weeks pretending to be a long-lost German friend. Most of the calls were in the middle of the night. Fortunately he thought it was funny..."
However, during the making of the fantasy epic trilogy, one of Viggo's jokes went too far and quickly escaladed into a "big crisis".
He to Live magazine: "On 'Lord Of The Rings' we had these little people who were stand-ins for the hobbits. One time Dominic Monaghan, who played the hobbit Merry, and I mimicked this one particular guy who had a really distinctive voice and rang the producers to say that all the little people were stranded on New Zealand's South Island with nothing to eat and no water. It became this big crisis and the producers sent everyone scrambling."