The Great Gazoo is a tiny, green, floating alien who was exiled to Earth from his home planet Zetox as punishment for having invented a doomsday machine, a weapon of immense destructive power. His invention was a button which if pressed would destroy the universe in an explosive "ZAM," though he insists he made it on a whim ("I wanted to be the first on my block to have one!") with no intent of using it. Gazoo was discovered by Fred and Barney when his flying saucer crashed; Gazoo recognizes Fred's and Barney's world as prehistoric Earth, implying Zetox banished him through time as well as space.
Gazoo refers to Fred and Barney as "dum-dums" and constantly causes problems for them. He can materialize and de-materialize objects, teleport, freeze time, travel through time, and perform other remarkable feats, but when he attempts to help out Fred and Barney, he usually ends up causing even more trouble. The only people who are able to see him are Fred, Barney, and the children, because they believe in him; animals also can see him. A running gag is that Fred argues with Gazoo while Wilma believes that he is talking to himself. When their daughter, Pebbles, says "Gazoo," Wilma thinks Pebbles is sneezing.
Gazoo appears in this film where he serves as an ally to Fred and Barney and he helps bring Fred, Barney, Wilma, and Betty together. Instead of being sent to Earth as punishment, he has to study humanity's mating habits because he is the most expendable of his people.
Gazoo was criticized for being an absurd character and that it didn't make sense for an alien to be in the series and he would've been better in The Jetsons. However, Gazoo did return in many commercials for Fruity and Cocoa Pebbles and comic books. Despite his unpopularity, Gazoo was one of the inspirations for The Fairly OddParents.