Elgyem is a light blue extraterrestrialPokémon with an oblong head with depressions on either side. It has black, symmetrical lines going down the front of its head. On the front of its head are shiny, green button-like eyes. Its hands have three finger-like digits: one red, one green, and one yellow. It has short, stubby legs and a small tail. Elgyem controls incredible psychic power, which it uses to squeeze its opponent's brains, causing them headaches. Its origin is said to be linked with a UFO crash site that appeared 50 years ago.
Overall, Elgyem has quite the welcoming and informative behavior. It is willing to help in stressful and otherwise difficult situations. However, Elgyem can become fully involved in something it feels to be important and protect that with its life. If Elgyem stands near a television, strange scenery will start appearing on the screen, which is said to be its home.
Elgyem debuted in A UFO for Elgyem! as the friend of Professor Icarus. It tried to help others by giving them visions of impending danger to help prevent the accident from occurring, but this only caused suspicion and drew attention to Professor Icarus's household. It befriended Ash and his friends when they too came to investigate and even saved Ash's life after showing them a vision of him falling through a weak board on a bridge. It was later kidnapped by Team Rocket, but Ash, Iris, and Cilan came to its rescue and reunited it with Professor Icarus.
Elgyem seems to be based on greys, one of the more popular kinds of alien. Its rocky physical appearance may be a reference to the stone circles of Europe, which were allegedly created by visiting extraterrestrials; or Japanese Dogū, statues which have often been confused for alien artifacts. The depressions in place of its ears look like craters on faraway planets. The round, colored fingers on its hands resemble the colorful faces of the invaders in the 1953 War of the Worlds film; however, the aliens in the film had green, blue, and red dots while Elgyem has red, green, and yellow. The flashing patterns of its fingers may have been inspired by the 1977 sci-fi film Close Encounters of the Third Kind, particularly the iconic scene where flashing color and sound patterns are used to communicate with the alien mothership.