Dragon was once an unidentified egg belonging to King Pablo. Although the king had always known that his egg would become a dragon, Pablo's knights were unaware of this until he hatched. Dragon currently resides at the top of Dragon Mountain. He acts similarly to a duck. Dragon cannot speak but manages to communicate through quacking noises.
Dragon is mostly a light green color, with dark green spots on his back. His horns are dark green with light green stripes. He has two large wings and white eyes with black pupils. On illustrated promotional art, Dragon's horns and spots are light purple. In books based on the series, Dragon's skin is teal blue.
Dragon has appeared in three episodes of The Backyardigans: "Tale of the Mighty Knights: Part 1" and "Tale of the Mighty Knights: Part 2" from season three, and The Tale of the Not-So-Nice Dragon" from season four. He appears in the theatrical performance The Backyardigans Live.
Dragon can also be seen in the following books: An Eggs-traordinary Adventure!, First Look and Find: What's Different?, Follow That Egg!, The Fantastic Flute, The Mighty Egg Sitters, and The Mighty Knights.