Dialga is a sauropod-like Pokémon. It is mainly blue with some gray, metallic portions, such as its chest plate, which has a diamond in the center. It also has various, light blue lines all over its body. It has a, somewhat, wing-like structure on its back, and a crest on its head, resembling a type of dinosaur. Dialga also has two horns on top of its head, two fang-like horns around its mouth, long claws, and a short tail, almost the impression of armor.
Dialga was created when Arceus hatched from its egg and created the world. Arceus tasked Dialga, Palkia, and Giratina to create time, space, and anti-matter. Dialga was worshiped as the master of time and metal, as it is a steel-type pokemon.
Dialga has the ability Pressure, which causes the opposing Pokémon to use twice as much PP for every successful hit.
Dialga has the ability to control time. Dialga, like many other Dragon-type Pokémon, can use many different elemental attacks. It is also one of the few Pokémon that can learn the move Aura Sphere. Capturing it gives an item called the Adamant Orb, which powers Dialga's attack.
In the manga, Dialga is being controlled by Cyrus and the red chain. Dialga uses its ability to control time for battling.
Dialga has no known gender, but in the Mystery Dungeon games, it is referred to as a male.
No other Pokémon has the same type combination as Dialga.
Dialga is the only Dragon-type Pokémon not to be weak to Dragon-type and Fairy-type moves.
Despite being able to levitate, it does not have the ability Levitate and thus remains susceptible to Ground type moves (unless taught Magnet Rise by the move tutor in Platinum).
In the anime, Dialga's rear spikes grow whenever it uses Roar of Time.
Dialga is the only legendary dragon in the quadrupedal class in the Pokédex. Palkia, Reshiram, Zekrom and Kyurem are bipedal, Rayquaza, Origin Giratina and Zygarde are snake-like, and Altered Giratina has six legs.
In Pokémon Mystery Dungeon: Explorers of Time and Darkness, Dialga was the one who created the Hidden Land. Ironically, he is also restricted from going back there when on an adventure.
The fact that Dialga has to rest after using the move Roar of Time may refer to releasing the power of time and stopping itself from moving.
Dialga, along with Palkia, may be based on the Shinto legend of Izanami and Izanagi, who are said to have created one island with a spear, erected a pillar on it, and from there created the islands of Japan. Appearance-wise, Dialga seems to be based on short-necked sauropod dinosaurs such as Camarasaurus or Brachytrachelopan with the aspects of diamond, a highly precious gemstone. How its type is Steel is possibly a reference to the aspect of timelessness and hence a supreme standing in the overall continuum of time; from the term "diamonds are forever", how metal is able to last, or the fact that most parts of a clock are made of metal, such as the gears. It may also be because diamonds are compressed carbon, and steel is a alloy from iron and carbon. Its turquoise pattern on its body is vaguely reminiscent to clock hands, interestingly, the ends of the "clock hands" are diamond-shaped.
Dialga is derived from "Diamond", as Palkia's is derived from the Japanese word for "Pearl". It may also be derived from dial, referring to its time-based capabilities.