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-Loompas are shown as African pygmies. Following growing controversy and criticism, in later editions of the book, Oompa-Loompas 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-Loompas would end up being preyed upon or attacked by Whangdoodles, Hornswogglers and Snozzwangers, which also lived there. Willy Wonka ended up inviting them to work at the Factory and get away from their natural predators. In the book, Oompa-Loompas 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-Loompas are only knee-high, with astonishing haircuts, and are paid in their favourite food, cocoa beans, which were extremely rare in their island. Oompa-Loompas 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-Loompas are also mischievous, love practical jokes, singing and are very good at improvising according to Willy Wonka. As each bad child makes his/her exit, the Oompa-Loompas sing moralising songs accompanied by a drum beat, and tend to speak in rhyme.thumb|300px|right
In the 1971 film Willy Wonka & the Chocolate Factory,, Oompa-Loompas are portrayed as orange-skinned. In the film, Vermicious Knids were also the enemies of the Oompa-Loompa alongside the Whangdoodles, Hornswogglers, and Snozzwangers.