Dragon is a young member of an airborne herbivore species of dinosaur who evolved over millions of years from carnivorous ground-dragons. He is Jane's best friend and is usually there when she needs him.
His words indicate he is at least 200 years old in the series. A tapestry created on the castle's creation (allegedly 300 years ago) depicts him as a hatchling.
Outside of the show, creators have described him as 300 years old (with a potential to live 1000) and born "about 300 years ago" in a cave not far from the castle. It is there that he meets Jane for the very first time. His home is actually in the mountain, full of secret tunnels and traps.
Dragon is an orphan, so he had to teach himself how to fly as well as other things to survive. As a baby he was captured by humans and kept as a pet, and was traded many times before escaping. He taught himself how to speak and stayed away from all humans, whom he would call a "short-life". After many years, he set out on a mission to discover more about the history of dragons.
Dragon saw a rune in the dragon language on his cave wall, that had been left by his father many centuries before, that indicated a child. Thinking Prince Cuthbert was that child, and that he may be able to help explain what happened to the other dragons (which had long since vanished), he swooped down and took him, hoping he could help decipher the runes. But the prince was no help at all. Meanwhile, at the castle, Jane realized this was her opportunity to finally use her secret training and she journeyed to the cave, with plans to slay Dragon. Soon, however, she realized Dragon was friendly and brought back the prince, to everyone's relief. The King, in gratitude, made Jane a squire—a knight in training.
After being discovered by Jane, he accompanied her and helped her with her goal of becoming a knight. He is also friends with Jane's friends Rake, Smithy, Pepper and Jester. Dragon enjoys toilet jokes, burning things, teasing Jane and her friends, lazing about the castle, and having adventures. Despite being centuries old, Dragon has a very childlike and innocent personality, and is extremely friendly. However, he can be very protective and quick to anger if he thinks his friends, especially Jane, are threatened, and he will consider any challenge to Jane's honor to mean a challenge to his own as well. Dragon is also known to be a very talented singer, possessing a splendid falsetto voice, though he does not like admitting it.
Dragon gets his ability to fly with such relatively small wings by storing the methane gas produced from the foods he eats.
The gas is stored inside two sac-like organs in his body. The lighter-than-air gas reduces his weight and allows him to fly surprisingly fast for a creature of his size. The drawback is that the very same gas also fuels his fire-breath. If Dragon were to use up his gas reserves in a fight (or a fit of sneezing) he would be unable to fly until he ate and produced more gas to replace what was used. He can help increase his potential for fiery breath by consuming raw iron. Both his sight and his hearing are far better than a human's. Though Dragon has been known to fly the other children around when needed or at Jane's request, he has never let any of the kingdom's adults ride him.
Dragon's scales often cause him great itching, which has been referenced several times in the series. Short-life weapons cannot pierce Dragon's skin, but is sensitive enough that Jane can tickle him. He has a very big heart (physically and emotionally). He is also very attracted to cows, and finds their general shape and behavior amusing, especially their mooing.