The Wheelers are scary obnoxious creatures that appear in L. Frank Baum's Oz books. They roll around the wastelands of the land of Ev annoying innocent people. They first appear in Ozma of Oz, in the chapter Letters in the Sand. Heres the description of them:
It had the form of a man, except that it walked, or rather rolled, upon all fours, and its legs were the same length as its arms, giving them the appearance of the four legs of a beast. Yet it was no beast that Dorothy had discovered, for the person was clothed most gorgeously in embroidered garments of many colors, and wore a straw hat perched jauntily upon the side of its head. But it differed from human beings in this respect, that instead of hands and feet there grew at the end of its arms and legs round wheels, and by means of these wheels it rolled very swiftly over the level ground. Afterward Dorothy found that these odd wheels were of the same hard substance that our finger-nails and toe-nails are composed of, and she also learned that creatures of this strange race were born in this queer fashion. But when our little girl first caught sight of the first individual of a race that was destined to cause her a lot of trouble, she had an idea that the brilliantly-clothed personage was on roller-skates, which were attached to his hands as well as to his feet.

"Run!" screamed the yellow hen, fluttering away in great fright.
"It's a Wheeler!"

In the film Return to Oz, the Wheelers are faithfully depicted, although they are given a bit more to do than in the books. The leader is played by Pons Maar, a comedic performance artist, who screeched and wheedled his way throughout the film. Dont worry, he gets his come-uppance.