Zetoxian

Zetoxians are a diminutive species of sapient, green-skinned humanoid aliens from the planet Zetox.

Biology
Members of this species are capable of highly-advanced feats, performing magic and reality warping at will. They move around by floating in mid-air.

They're also capable of selective invisibility; being visible only to some people.

Notable members

 * The Great Gazoo: A Zetoxian who was exiled to Earth in prehistoric times and made friends with the local "cavemen", or primitive Humans.

History
The Great Gazoo was banished from his homeworld of Zetox as a punishment for creating a doomsday device, so powerful that it could possibly destroy the universe. Gazoo claims that he never intended using it, although he jokingly states that "I was the first one on my block to have one".

Gazoo is only seen by his cavemen friends Fred and Barney, and their young children Pebbles and Bam-Bam. The other Humans are apparently unable to see him because they don't believe in his existence.