Night Fury

The Night Fury is a species of dragon. In the movie adaptation of How to Train Your Dragon, Hiccup's dragon Toothless is a Night Fury dragon. Night Furies are large, sleek, black, have retractable teeth, and breathe blasts of blue fire which explode on impact.The Night Fury is the rarest species and the most intelligent. Unlike most dragon species, Night Furies have a short neck and lack a nose horn. Before Hiccup knocked Toothless out of the air at the start of the film, none of the Vikings of the Hairy Hooligans had ever seen or fought a Night Fury. This is likely due to the Night Fury's dark color and blue fire (which offers less illumination), which makes it virtually impossible to see at night, which is when it attacks. Additionally, since Night Furies never steal food, they never actually land.The Night Furies most powerful form of attack is to dive bomb it's target by folding it's wings over it's stomach,and dives.At the last second it blasts out a large ball of fire,opens it wings,and disappears into the night as it's fireball hits it's target and makes a huge explosion

How Dreamworks came up with "Night Fury"
When Dreamworks started the project How To Train Your Dragon, they wanted the dragons to look more like real animals, and not like the basic lizard-like, green-scaled dragons seen in most movies and books. Therefore, Dreamworks decided to mix different kinds of animals to create the dragons you see on screen. Since Toothless is being trained by Hiccup during the movie, Dreamworks wanted to create a dragon that was more pet-like and familiar to the audience. It is said that the Night Fury is a mix between a cat and a dog. The "cat-like" parts may refer to the Night Fury's pointed ears, yellow-green slit-pupiled eyes,which can go round sometimes and swift, slinking movements. The "dog-like" parts may be in it's smaller stature and friendlier behavior. Simon Otto, head of Character Animation on How To Train Your Dragon, says, "When watching the film with the rest of the crew, we realized that 'dog people' think that Toothless is just like their dog and 'cat people' think he's definitely a cat.'" Interview with Simon Otto, Head of Character Animation at Official How To Train Your Dragon Tumblr.

The Night Fury also bears a striking resemblance to the Disney character Stitch: The head, teeth, ears, paws and claws are very similar in appearance, as well as his playful attitude. It is not known if the Night Fury was derived directly from Stitch, or if both characters were simply derived from the same, cute and familiar animals; cats and dogs. It is not impossible, though, considering that Chris Sanders and Dean DeBlois, the directors of How to Train Your Dragon also directed Lilo and Stitch.

Trivia
Hiccup's Night Fury Toothless has a red leather tailwing with a skull on it at the end of the movie.