Elliott is the titular deuteragonist in Disney's 1977 film Pete's Dragon. He, as the film's title suggests, is a large green dragon who befriends a young orphan named Pete.
Elliott is a dragon with the ability to become invisible. He is depicted as a benevolent character who assists children in need, like Pete. He is shown to be fairly clumsy, even when flying. He is also shown to be very protective of Pete.
Elliott is apparently a guardian of children, coming and going, seeking those who are in need of a friend, at least until they have a family who can be there for them or helps those he befriends until their problems are all resolved. Once a child has no further need of him, he sadly moves on and never sees them again, so it's possible he is really a guardian spirit whose purpose is to protect and help children.
The Protectors of the Multi-Universe
Elliott becomes David's companion and protects him along with Abigail and Olivia. He also helps the Children of the Autobots to protect the children and those who still believe in Disney and dreams.