Legend of the Boneknapper Dragon

Legend of the Boneknapper Dragon is a 2010 animated short film by DreamWorks Animation that is a sequel to the feature film, How to Train Your Dragon.

The film opens with Gobbers house on fire and the Vikings and resident dragons getting it under control. Gobber is convinced that his old nemesis The Boneknapper Dragon, a giant, yet perfectly silent dragon the only one with no roar that clothes itself in bones for armor, is responsible. However no one else believes that the Boneknapper even exists, much less that it burned his house, especially when the evidence suggests that the fire was started by his underwear drying at his hearth and catching fire.Undeterred, Gobber vows to hunt down the beast once and for all and Hiccup reluctantly decides that he cannot let his mentor go alone, so he convinces his Viking recruit comrades to join him as well. As the gang row to the island where Gobber believes the dragon lives, Gobber tells them of his past encounters with the monster, shown to the viewer in traditional animation. He apparently first met it when he discovered a group of frozen Vikings after he relieved himself on an iceberg during a family outing and he extracted a small treasure chest from the ice. As the frozen Viking he stole it from resisted by punching him in the face a couple of times, the Boneknapper appeared and chased him until he landed back in the family boat. The contents of the chest turn out to be a small bone that Gobber has since used as a belt buckle. ........

Source: Wikipedia