In Legend of the Boneknapper Dragon, Hammerhead Sharks (Family: Sphyrnidae) have the classic shark dorsal fin, a two-tone grey body, and eyes that only protrude from the head a little. Their fins are tipped with black. They appear to only have one row of teeth that look somewhat mammalian.
In actuality, Hammerhead Sharks are typically located in more temperate and tropical waters, rather than the cold Northern oceans and seas. Vikings are unlikely to have come across one, except possibly while away from Scandinavia on trade journeys. Many species have much smaller eyes and longer cephalofoils, or "hammers".
In the Movie short, Hammerhead Sharks are seen gathering around Gobber in large numbers to do him harm or perhaps just eat him. They are portrayed in large numbers to give Gobber's story a larger than life feel - a tall tale. In reality, Hammerhead Sharks do in fact school together, most often in the daytime, and also when migrating. They do not, however, school to attack terrestrial creatures (unless an injured one falls in the sea!). Hammerheads are generally not aggressive, though three species have been implicated in attacks on humans.
In the How to Train Your Dragon Franchise, Hammerhead Sharks only appear as an obstacle in Gobber's story that he must overcome. There is no indication of these sharks being part of the How to Train Your Dragon Viking diet. However, in theory, if a historical Viking fished up a Hammerhead Shark, they may very well have eaten it. Hammerhead shark is eaten in many parts of the world where it occurs.
They appear in the short Legend of The Boneknapper Dragon. Their role is brief, but they appear in schools and try to attack Gobber. He escapes the Boneknapper by island hopping; using the sharks' heads as stepping stones, and stopping only long enough to brush one of the shark's teeth.
- Gobber's tale becomes increasingly unrealistic, including both a Hammerhead Yak and a Hammerhead Whale.
- Based on the tiny islands and their flora Gobber is stranded on in the Hammerhead Shark sequence, it is possible he may have actually journeyed to a place with a more tropical climate, and where Hammerheads might actually occur