The Great Gazoo is a tiny, green, floating alien who first appeared in The Flintstones animated series in 1965. He was banished to prehistoric Earth from his home planet Zetox in 2000 AD, as punishment for having invented a doomsday machine. He can materialize and dematerialize objects, teleport and manipulate time. The only people able to see him are Fred, Barney, and the children, because they believe in him; animals can also see him.
Note: Gazoo was introduced midway through the show’s final season and is often cited as an example of The Flintstones having “jumped the shark.” In all, Gazoo appeared in 11 episodes, and was basically the nail in the show’s coffin. “Toodle-loo, dumb-dumbs!”