This quote is currently sourced through second-hand news blurbs and the date of the magazine, while probably December 2009, is currently unknown.

He added 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.”

Example Sources:

http://www.inquisitr.com/51025/viggo-mortensens-prank-on-elijah-wood/

http://breakingnews.iol.ie/entertainment/mortensen-reveals-prankster-games-on-trilogy-437251.html