Porygon-Z

Porygon-Z (Japanese: ポリゴンZ PorigonZ) is a -type Pokémon introduced in Generation IV.

Physiology
Porygon-Z's appearance is similar to that of Porygon and Porygon2, though darker in color when compared to both of them. It has a very smooth appearance much like Porygon2. It's head is not attached to its body and is now upside-down with a slight tilt. It has a blue beak, and yellow eyes with a bull's eye target pattern in them. Its legs now appear to be more wing like, while its tail points downward rather than up. The spot of blue that was located on its chest now goes across the chest, connecting the two wings.

Natural abilities
Porygon-Z have the abilities Adaptability or Download. Adaptability allows the power of a move, with the same type as it is, to be doubled in battle. The ability Download will raise either its Attack stat or Special Attack stat by one stage depending on foe's lowest defensive stat.

Aside from that, the programming added to create Porygon-Z was intended to allow it to upgrade into a better Pokémon, but as a result, Porygon-Z began to exhibit odd behaviors and the data used to program it became glitched giving it its odd appearance.

Porygon-Z is also notable for having the highest Special Attack, one of two statistics that influence the power of an attack, among non-legendary Pokémon. It shares this feature with another Pokémon, Alakazam.

Evolution
Porygon-Z evolves from Porygon2. A Porygon2 can only evolve into a Porygon-Z when it is traded with a Dubious Disc.

Game Info
Porygon-Z first appeared in the Generation IV games. It is only obtainable through a trade. During a trade, a Porygon2 must be carrying a Dubious Disc with it, this is what triggers its trade evolution.

Porygon's evolutionary line is notable for being the only evolutionary line that contains two evolutions triggered through trading.

Trivia

 * Porygon-Z is the second non-legendary Pokémon to have the highest base Special Attack (surpassed by Chandelure), and is tied with Alakazam and Volcarona.
 * It is the only Pokémon whose Japanese name has a foreign character in it.
 * Porygon-Z and Porygon2 are the only two Pokémon that have not appeared in the anime.
 * When Porygon2 turns into Porygon-Z, two stats bcome lower Def. and Sp. Def.