Inkay is a primarily blue squid-like Pokémon. It has a transparent mantle that resembles a hat with a pink "inner body" overlaid with yellow lights. It has two tendril-like tentacles that hang from this "hat", similar to some styles of winter hats, and these tentacles hang next to its six short arms. Its eyes are round and have pupils, but no identifiable iris. Inkay also has a small, pink, beak-like mouth set between its eyes.
Those who stare at its body lights become dazed and lose their will to battle, allowing Inkay to escape. Inkay can also use these light-emitting spots to send messages in the form of complex flashing rhythms. It and its evolution, Malamar are the only known Pokémon capable of learning Topsy-Turvy.
Multiple wild Inkay appeared in Facing the Grand Design!, where James's Inkay helped save them, as well as some good Malamar, from the evil Malamar. James tried to release Inkay afterwards so Inkay could be happy with the other Inkay, but Inkay refused and rejoined his team.
Xerosic's Malamar was revealed to have been under his ownership since he was an Inkay. He evolved when Lysandre explained his peculiar evolution method and demonstrated it by turning Inkay upside-down, making him evolve instantly. He showed up in a flashback in Chesnaught Protects.
In the Pokémon - The Legend of the Dragon King manga
Inkay appears as a Poké Ball summon in both versions of the game. It turns over and hits the ground, making all opponents who are on the ground trip.
NA: Inkay may look like a Water-type Pokémon, but it's actually a Dark/Psychic type! Once it has reached the proper level, Inkay can evolve into Malamar if you hold the Nintendo 3DS upside down. In Smash Bros., its Topsy-Turvy move will flip anyone who wanders too close upside down. Watch out!
PAL: A Pokémon that looks this much like a squid MUST be a Water-type, right? Wrong! It's a Dark- and Psychic-type. If you're struggling to get it to evolve, try holding your system upside down. In this game, Inkay's Topsy-Turvy move can knock you over, and you won't be much use like that, so watch out!
In addition to Inkay's method of evolution into Malamar being unique, it would have been impossible in any of the previous core series Pokémon games, because the Nintendo 3DS is Nintendo's first handheld system with an internal gyroscope.