Inkling

Inklings are a sentient race of squid-like humanoids who are the main protagonists in Splatoon.

Background
Inklings are evolved species of [Squid] that came to be after global warming sunk human civilization. ~1000 years before the events of Splatoon, the inklings crawled up to what little land there was left.

2000 years before Splatoon, the Turf War was established. The original Turf Wars were judged by Judd who was cryogenically frozen from the time of the humans.

100 years before the events of Splatoon, the Inklings and the Octarians engaged in a great Turf War. A young Cap'n Cuttlefish and the Inklings won, forcing the Octarians to retreat into Octo Valley.

Appearance
Inkings can alternate between a humanoid form and a squid form. At the age of 14, Inklings gain complete control over both these forms and can change at will.

The squid form resembles a small, flat, monochromatic squid-like being with four small tentacles in the middle, and two large ones on the sides, resembling the hair of their humanoid form. It has relatively large head fins, and two upward-facing, human-like gray eyes. The undersides of their enlarged calipers are always white, regardless of what colour the rest of them is. In this form, they are largely incompetent outside of their own ink, but when swimming in it, they can completely submerge into it and swim at speeds almost four time their humanoid form. They can even jump out of the ink to cover further distances and swim up ink-covered walls. However, this form is also largely vulnerable, as being inside of enemy ink in this form will instantly kill the Inkling.

The humanoid form has a black marking for supposed "swim goggles" around its eyes, pointed ears, and "hair" that resembles a squid's tentacles that changes colour according to their ink color, is randomly selected out of pairs that you can see in Sunken Scroll number seven. Their mouths contain human-like teeth, as well as three larger sharp teeth which resemble a squid's beak. Inklings have no bone structure, making their teeth possibly the only truly solid part of their body, as squids also have teeth.

Inklings are also customisable. If the player chooses a girl inkling, their inkling will have thin eyebrows and two long, strand-like tentacles that hang from both sides of the head, and four extremely short tentacles in the back. A boy inkling has noticeably larger eyebrows and all six tentacles tied in a ponytail in the middle of the back of its head, appearing to be tied together with a band. Each inkling has six hair-like tentacles, along with four others as their arms and legs. Skin color, gender, and eye color can be changes in the options menu at any time. Head accessories, shirts, shoes, and weapons can be changed to the player's liking in the equip menu. Many clothing items change to match the Inkling's current colour. Both forms have a slightly different pitch to their voice.

Abilities
Both of the Inklings' forms have abilities associated with them. In humanoid form, Inklings can splatter a special type of coloured ink by using various weapons, such as a gun that resembles a Super Soaker water gun. This ink can be quickly spread over many surfaces, with the exception of green barrel-like objects, black pavement, and glass surfaces. This ink can inhibit the movement of Inklings that do not have a matching colour. When used as a projectile, ink can damage opposing Inklings. In squid form, an Inkling can swim and jump quickly through ink of the same colour, using this mechanic to swim up walls and through wire fences and grates into areas that are not typically reachable. However, squids cannot travel past striped barriers, preventing them from swimming into inaccessible areas. While squids form inklings are in their own ink colour they will be invisible if they stay still and when moving only slight ripples will appear. While in ink, they will also gain more ammo or paint the humanoid inkling can fire. When squid form inklings are on land without paint, they will be very visible and move very slowly, even slower then a humanoid inkling.

Inklings are unable to swim in water. When underwater, their form dissolves for unknown reasons. The official American Splatoon Tumblr has mused that this may be because their bodies are actually made of liquid. Another reason to support this is that squid form inklings can go through grates.

Death
There are three known ways an Inkling can die. They can die from water, enemy Ink, and falling off of a ledge. When they die in water, they dissolve. When they die from enemy fire, the inkling's weapons and gear will fall to the ground, while the inkling will explode in the enemy's colour. When they die like this, a ghost that looks like the squid form inkling, will float into the air. Also, if they fall of a cliff, they will explode as well, but in their ink colour. When an Inkling dies, it will respawn at the Respawn Point or at the Check Point if they are playing in Hero Mode.

Trivia

 * According to the EDGE article, Inklings get full control of their squid and human forms at age 14. Since the playable Inklings seem to have full control of their squid and human forms, one can assume that they are at least 14 years old.
 * An Inkling's ink colour is random online, while in Hero Mode, it depends on the chapter.
 * The developers said when they came up with the concept, they didn't consider Bloopers from the Mario series, despite the close resemblance between Bloopers and Inklings.