Oompa-Loompas are known for their short stature, green hair, orange skin and white pants with protruding knees. In early editions of the novel, Oompa-Loompa are shown as African pygmies. Following growing controversy and criticism, in later editions of the book, Oompa-Loompa are white skinned and golden haired. Oompa-Loompa come from Loompaland, which is a region of Loompa, a small isolated island in the Atlantic Ocean. The Oompa-Loompa would end up being preyed upon or attacked by Whangdoodles, Hornswogglers and Snozzywangers, which also lived there. Wonka ended up inviting them to work at his factory and get away from their natural predators. In the book, Oompa-Loompa are the only people Willy Wonka will allow to work in his factory, because of the risk of industrial espionage committed by his candy-making rivals. Oompa-Loompa are only knee-high, with astonishing haircuts, and are paid in their favourite food, cacao beans, which were extremely rare in their island. Oompa-Loompa insist on maintaining their native clothing: men wear skins, women wear leaves, and children wear nothing (in the 1971 film, the Oompa Loompas wore Germanic clothing with stripped shirts and baggy lederhosen-like pants, in the 2005 film, the Oompa Loompas wore tribal clothing in their native Loompaland and typical factory worker uniforms in the factory). In the 1971 film the male Oompa-Loompas are seen working in the factory, in the 2005 film only one female worker, a secretary Mr. Wonka addresses as Doris (when the Great Glass Elevator passes through the administration offices) is seen, though in Quentin Blake's illustrations both male and female Oompa-Loompas are shown rolling away Violette Beauregarde after her transformation into a blueberry. Presumably the females remain in the village seen briefly from the Great Glass Elevator.
Oompa-Loompa are also mischievous, love practical jokes, singing and are very good at improvising according to Wonka. As each bad child makes his/her exit, Oompa-Loompa sing moralising songs accompanied by a drum beat, and tend to speak in rhyme.
In the 1971 film Willy Wonka & the Chocolate Factory,, Oompa-Loompa are portrayed as orange-skinned. In the film, Vermicious Knids were also the enemies of the Oompa-Loompa alongside the Whangdoodles, Hornswogglers, and Snozzwangers.