In the Book
Toothless is Hiccup's hunting Common or Garden Dragon in the book series, who likes to cause mischief when he can.
Physical Appearance & Personality
Toothless is much smaller than any of the other young Vikings' dragons. He is a young Seadragonus Giganticus Maximus, as discovered in How to Betray a Dragon's Hero, although it was originally believed he was an incredibly small Common or Garden Dragon (although Toothless was convinced that he was ah rare breed of Dragon called a Toothless Daydream). As Toothless's name suggests, he has no teeth. He is portrayed as being a dark green color with red membranes in his wings. He is also small enough to sit on Hiccup's arm with relative ease. Toothless is incredibly disobedient, and like all dragons very selfish and ungrateful, he is nonetheless quite attached to Hiccup. However, Toothless' behavior does have its drawbacks, especially when he manages to cause the entire young generation of the Hairy Hooligans to be forced into exile by starting a fight at Thor's Day Thursday celebrations.
To prevent Hiccup's father from being furious over how small and average his son's dragon is, Hiccup's best friend Fishlegs comes up with a legend that Toothless is not a Common or Garden dragon, but is, in fact, a very rare breed called Toothless Daydream and is possibly an offspring of a great dragon-leader, King Daggerfangs. From then on, Toothless always claims that legend to be true.
Toothless and Hiccup
Although selfish, Toothless is actually very attached to Hiccup. He even has a usual sleeping place in Hiccup's waistcoat. While he doesn't always listen, Toothless always manages to come through in the end. Whenever Hiccup is is in trouble, he takes it upon himself to save his human. When the Red Rage attacked Flashburn's school, Toothless was temporarily overcome by power and fury. Hiccup's call for his dragon snapped him out of it and helped his master escape. Toothless doesn't really like the idea of sharing Hiccup either. He was jealous of Wodensfang when he saw him in his spot in Hiccup's waistcoat, but they eventually become friends.
Toothless also has a huge crush on Stormfly, Camicazi's Mood Dragon. He often spends time with her and tries to impress her.
Role in the books
At the eastern coast of Berk is an area known as Wild Dragon Cliff, Hiccup uses a dragon basket to capture a dragon for himself. Fishlegs escapes the area without a dragon, meaning he is at risk of exile. Hiccup runs back in to the cave to get another for him and the two leave with a dragon each (Horrorcow and Toothless).
After returning home, Hiccup attempts to train Toothless based on advice from Gobber, but this turns out to be problematic as Toothless's disobedience causes Hiccup's many attempts to fail, eventually forcing him to resort to pampering. During practice for hunting with Fishlegs, Toothless finally agrees to be co-operative on the condition that he is told one joke for every fish he catches.
On Thor's Thursday, during the final part of the rite of passage, Toothless offends Fireworm (Snotlout's dragon) and there is a huge fight between them all. This means that the younger Vikings have all failed their rite and will be exiled. However, it is not long before 2 giant Sea Dragons arrive with a storm and Hiccup is turned to for help to speak with the dragon. When Hiccup tells the Elders of the remaining dragon's plan to eat them all, Hiccup decides to use this time to gather the boys and their dragons together and come up with a plan to stop the Green Death from killing anyone. Toothless decides not to go along with this as he thinks the plan is suicidal and he dislikes the giant dragon a great deal.
The plan seems to be working until Hiccup is swallowed whole by the Green Death. When Toothless sees that all the wild and domestic dragons have left out of fear, he concludes Hiccup is his only remaining family and saves him by making the Green Death sneeze. Hiccup eventually makes the dragon explode, causing him to pass out.
