Vermicious Knids (Knid is pronounced K'nid) are a species of amorphous, shape-shifting aliens that invade the Space Hotel USA in Roald Dahl's Charlie and the Great Glass Elevator, the sequel to Charlie and the Chocolate Factory. They are also mentioned in the 1971 feature film adaptation, Willy Wonka & the Chocolate Factory, except on this occasion they are referred to as being one of the species of animals that inhabit Loompaland.
In their natural form, Vermicious Knids are huge, dark, egg-shaped beings that are quite at home in the vacuum of space. Their homeworld is the planet Vermes, a planet located (as stated in dialogue) 184,270,000,000 miles away from Earth (this would place it at 52 times Pluto's distance). Their one weak point is that they are show-offs; they cannot resist shaping themselves to spell the word "SCRAM" - the only word they know - before they attack. Willy Wonka knows that this interval is ideal for escaping an encounter with the Knids.
According to Willy Wonka, numerous sentient alien species that formerly existed have been wiped out by the Knids' predations. Wonka claims that the only reason humans have escaped this fate is because the Knids - not being heatproof and not possessing retro-rockets - cannot enter Earth's atmosphere without being burned up by friction. What are supposed to be shooting stars are in fact shooting Knids burning up in the atmosphere. In Charlie and the Great Glass Elevator, Wonka destroys the swarm of Knids by burning them in Earth's atmosphere.
When Nestle created their interpretation of Wonka's world to sell chocolate bars under the name "Wonka", they released a number of downloadable flash games. In all these games, Knids seem to have entered the factory and have the appearance of a flying green blob with a single red eye.