Meltan

Meltan is a Steel-type Mythical Pokémon from an unknown region. It evolves into Melmetal when fed 400 candies.

Trivia

 * Meltan was first teased after the September 2018 Community Day on September, 2018. Then it was officially revealed on September.
 * Meltan was originally unavailable for capture, but it appeared in the wild as a disguised Ditto.
 * Meltan and its evolution are the first and only Pokémon to debut in Pokémon GO before any other Pokémon game, including the main series.
 * Most of Meltan's body is made from liquid metal, and its shape is very fluid. It can use its liquid arms and legs to corrode metal and absorb it into its own body.
 * Meltan generates electricity using the metal it absorbs from outside sources. It uses this electricity as an energy source and also as an attack that can be fired from its eye. Despite this, Meltan and its evolution are not Electric-type.
 * Clearly a curious Pokémon, Meltan is very expressive and shows an interest in all kinds of things.
 * Meltan and its evolution are the only Pokémon to classified under as being from Unknown origins in Pokédex.
 * Meltan is the only Mythical Pokémon that can evolve.
 * Meltan and and its evolution are also the only Mythical Pokémon that can be transferred, traded, and be deployed as Gym defender.
 * Its name was originally displayed as "???" in gameplay and in game data it was referred either as "Pokémon 891" or "Kecleon", the second one was because of Meltan being initially released in the game by replacement of Kecleon assets before its own were added to game files.
 * Additionally, following names were given for this Pokémon in player community before its official name was announced: "Nutto", "Nutface", "Incogditto", and “DittoNut”. All of these nicknames refer to either its nut-shaped head or its resemblance to Ditto.
 * Its small, silver body resembles Ditto and a hardware nut-shaped head with an eye floating inside, which when displayed in nearby as shadow silhouette resembles Unown.
 * Before Melmetal was revealed there were speculations that Meltan would have an evolution form, as there were sound files in game data hinting it as well as mysterious shadow at the end of Pokemon Let's Go: Meltan Evolution Teaser Trailer.
 * There are sound files of Meltan's and Melmetal's cries in game assets. These files are called "pv891.wav" and "pv892.wav" and they implied that Meltan's National Pokédex entry number could be 891, which could confirm at least 86 new Pokémon species introduced in Generation VIII of the core games series, however after final release of this Pokémon to the game its Pokédex number was revealed to be #808.
 * Meltan Candies can be acquired by sending Meltan from Pokémon GO to Pokémon: Let's Go which is strongly recommended since Meltan like all Mythical Pokémon cannot be selected to mass transfer.
 * Professor Willow said that his buddy is Meltan.