Take this How to Train Your Dragon Quiz! Easy Trivia | Movies

Answer: Vikings believe that a hideous name would frighten off gnomes and trolls.

Hiccup tells us this in his voice over at the beginning of the film, when he is introducing himself and his people, and describing the place where they live. He finds it ironic because anything not frightened by the Vikings' nature wouldn't be worried about a name.
At a later point in the movie, while talking to Hiccup's father, Gobber points out that trolls do exist and they are notorious for stealing left socks.

Answer: the Night Fury

While the "Dragon Manual" has drawings and descriptions of many different types of dragons, the page for the Night Fury is blank. No one has ever been known to see this dragon because it is so fast and never misses its target.
Without the strength needed to pick up the normal arsenal of weapons, Hiccup has invented a catapult-type machine that throws a set of bolas. The first time he uses it he hits another Viking, but the second time he hits a Night Fury. The problem is, no one believes him.

Answer: the dragons' home

The dragons' raids have severely depleted their food supply. Stoick decides that he has to try and deal with the dragons once and for all by destroying them at their source, even if 'some of them won't come back'. He doesn't get a lot of volunteers at first, until he says that those left behind can look after Hiccup. More enthusiasm is shown for the trip after that. Before he goes, he gives permission for Hiccup to begin dragon training with the other youths. Ironically, Hiccup is no longer interested in learning to kill dragons.

Answer: It is missing part of its tail fin.

Hiccup watches the dragon's frustration as it tries to fly out of the gorge. It reaches a certain height and then spirals out of control. Hiccup's initial sketch of the dragon shows it with two flaps (for want of a better word) at the end of its tail.

He them rubs one of these out. Later in the film we see him sketch in the second flap, as he understands that there should be two. He then makes a prosthetic flap, which he is able to control from the dragon's back, which allows it to fly.

Answer: His new understanding of dragons gives him insight on how to befriend them in dragon training.

During dragon training, the trainees are given various tasks that involve subduing or eluding different types of dragons. Understanding that they are not killers by nature, Hiccup is able to subdue them with touch and tickles, making him the star of training. All the other kids, who previously shunned him, want to sit beside him during meals.
He actually graduates at the top of his class, winning the distinction of being able to kill his first dragon in front of everyone. The only problem is, he no longer wants to kill a dragon.

Answer: The place where the dragons take their plundered food

During their ride, they get caught up in a flock of dragons that are all returning to an island. Once there, the dragons fly into a cave where they drop the food they have been carrying down a hole. Astrid makes a comment about how their stolen food is being wasted, just before they see a dragon drop a very small amount of food down the hole. An enormous dragon's head pops up and eats the dragon that did not bring enough food.
Hiccup realizes that the dragons are only stealing livestock from the village in order to feed this massive dragon and avoid being killed themselves.

Answer: a helmet

The helmet is a metal cone with horns attached. Stoick informs Hiccup that it was once half of his mother's breastplate and Stoick is wearing the other half, as a way of keeping her close. Hiccup looks less than thrilled with this fact and thanks his father for the breast... ah, hat.

Answer: No

When Stoick realizes that Toothless has taken Hiccup to the dragons' home, he lashes Toothless to the ship and forces the dragon to take him there. Hiccup doesn't want Toothless or the Vikings hurt, so he gets the kids to ride the dragons that they used for dragon training to the island. Once there the kids set about fighting the monster dragon, which has been drawn out of its lair by the Vikings, who punched a hole in the side of the mountain with a catapult. Fishlegs is sent to check for the dragon's blind spot. During this endeavour, the dragon opens up two rows of extra eyes and Fishlegs announces that the dragon doesn't have a blind spot (due to multiple eyes).

Answer: Toothless shoots a fireball down its throat.

Earlier, in dragon training, Hiccup had mentioned that dragons weren't fireproof on the inside. This observation was made when one dragon reacted poorly to a small fireball being shot down its throat. Hiccup remembers this and has Toothless aim a huge fireball down the monster's throat, which brings it down.

Answer: his left foot

We get a sense that something is wrong when Stoick thanks Toothless for saving his son and Gobber chimes in with "Most of him."
When Hiccup gets up out of bed, he finds that his left foot has been replaced with a metal peg, which Gobber says he made for him. Gobber says that he hopes that Hiccup likes it and Hiccup, forever the tinkerer and inventor, replies that he will probably make some alterations of his own.