Flying Saucer

Flying Saucers, often called U.F.O.'s or Unidentified Flying Objects, are spacecraft that are piloted by Aliens. They are capable of hovering in one place, but have enough thrust to escape Earth's gravity and fly in space. Although usually said to have futuristic weapons, none of the ones on Arthur have had any weapons at all. Some do, however, have tractor beams, although people do not get hurt by them.

Flying Saucers mostly appear in the kids' imaginations, especially Buster, but as aliens are real, so are they (although the kids never notice them).