The short was originally broadcast on television on October 14, 2010 on Cartoon Network, and released as a special feature on Blu-ray and double DVD edition of the original feature film on October 15, 2010.
The film follows Hiccup and his young fellows accompanying their mentor, Gobber, on a quest to kill the legendary Boneknapper Dragon.
The film opens with Gobber's 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 dragon that clothes itself in bones for armor, is responsible. However no one believes him, 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 and Hiccup decides that he cannot let his mentor go alone, and convinces his comrades to join him as well. As the gang row to the dragon's suspected island, Gobber tells them of his past encounters with the monster. He apparently first met it when he discovered a group of frozen Vikings during a family outing and he extracted a small treasure chest from the ice. As the frozen Viking he stole it from resisted, the Boneknapper appeared and chased him until he landed back in the family boat. The contents of the chest turned out to be a small bone that Gobber has since used as a belt buckle.
The stories continue, becoming increasingly ridiculous as Gobber tells of later encounters being interfered with by hammerhead sharks, hammerhead whales and hammerhead yaks in different combinations. Unfortunately, the group's attention is so occupied that they allow their boat to run aground and sink. Taking the loss of their means home in stride, Gobber sets up a trap using Fishlegs, disguised as himself, as bait. Unfortunately, the Boneknapper silently comes up from behind the group and Fishlegs cannot warn them until it is in position to attack. The gang have to take shelter in their trap and Hiccup sees an empty spot on the dragon's armor that exactly resembles Gobber's belt buckle bone. Hiccup realizes that the dragon may simply be seeking it to complete his armor.
However, Gobber refuses to listen his proteges' advice to give up the bone to placate the creature and he is soon seized in the beast's jaws. Finally, as he is thrown up into the air, Gobber decides to surrender the bone and throws it at the dragon. The bone lands perfectly in the empty spot and the dragon is finally able to triumphantly roar with his completed armor.
As it turns out, the satisfied dragon is a friendly one with his completed quest, and it agrees to fly the adventurers back to Berk. Furthermore, Fishlegs observes that the dragon's roar is a mating call and Gobber notes that he will certainly be believed now, with multiple boneknapper dragons following them home.