Toothless

Toothless is the only Night Fury seen thus far in the franchise, so his physical appearance is all that can be studied to learn about Night Fury anatomy. He has jet-black scales covering his whole body. In the beginning, his sides and wings have small light patches in a pattern similar to that of a manta ray. By the second film, these patches have faded, and by the third, completely removed, with Toothless' coloration now being solid black. Toothless possesses two sets of wings (one main pair and one smaller pair near the base of his tail). The first pair allows him to do a vertical take-off. Behind that is a set of smaller wings that aid in his gliding. At the end of his tail, he used to have two natural tail fins that aided in steering and stability, but he is missing the left side of his tail fin, which was lost when Hiccup took Toothless down with his Mangler. This is later replaced by a mechanical fin that Hiccup constructs himself. As such, he is often seen donning the fin and its complementing saddle.

Toothless has a large scar on his right shoulder/neck which is around a foot in length with the width of about an inch. He also has a scar on his left front leg. Toothless' eyes are bright green, sometimes acid or emerald-green. They are located very near the front of his face giving him excellent depth perception and reflexes in flight. He can narrow his pupils to slits when threatened or angry, similar to a cat. However, when he is docile or happy, his pupils dilate and become more dog-like. Toothless gets his name from his ability to retract his teeth into his gums.

Toothless is the most intelligent of all known dragons, and seems to have a dry sense of humor, similar to that of Hiccup. When Hiccup released him, he did not kill Hiccup, as it is possible that he sensed goodness in the boy, or that he was simply repaying the favour by leaving him alive. He was still very wary and would not let Hiccup near him for several days.

He doesn't take kindly to being offended and is very protective of his human friend. He is usually quite playful and even a little teasing. He shows a sense of great curiosity, imitating Hiccup's actions and mannerisms when they initially encounter one another and can understand Hiccup's words and commands as well as agree with some of what he says. It is shown that he has become aware of Hiccup's relationship with Astrid, even seeming to briefly tease him about it, even though he did somewhat create it with the Romantic Flight scene in How to Train Your Dragon, which Toothless did to get Hiccup and Astrid together.