Ditto (メタモン, Metamon), is a fictional creature from the Pokémon series.
Ditto is a Normal-type Pokémon introduced in Generation I, and is categorized within the Pokédex at #132 as the "Transform Pokémon". Its only move in every game is Transform which allows it to turn into a copy of its opponent, though while keeping its own original HP. The effect disappears when switching out or finishing the battle. In Generation V it received the Hidden Ability Imposter, which makes it transform automatically upon entering the battle.
While Ditto copies the Pokémon's actual coloring in Generation III onwards, the purple coloring of the copied fighter in Ultimate pulls from Ditto's appearance in Generation II, where it would transform into a purple copy of the opposing Pokémon. This also applies to Generation I when played on a Super Game Boy.
As a Poké Ball Pokémon
Ditto is a Pokémon that was removed from Super Smash Bros. Melee just prior to its release. Its purpose was to create an AI copy of the user's character, which would aid them in battle. The reason for the removal of Ditto is unknown; however, it did have an entry in the game's official strategy guide, suggesting that Ditto was a late cut to Melee.
Ditto can still be accessed using the debug menu through an Action Replay, where it is known internally as METAMON. When summoned from a Poké Ball, it simply says "Mon-mon!", stretches out while spinning, then disappears. It also deals around 7-8% damage to whoever touches it while it is spinning, with weak knockback.
As a Tournament Mode element
In Tournament Mode, in either Winner Out or Loser Out style tournaments, when selecting a character for these events, the player can hold down L+R and then press A to select a random character. The character will appear as Ditto and will be a random character and color when each match begins.
Ditto is featured as a collectible trophy, randomly obtained in the Trophy Lottery.
Every Ditto has the ability to copy a Pokémon's entire cell structure in an instant and become its exact replica. They're terrible at remembering techniques, but when they use Transform, they temporarily learn all of their foe's moves. If a Ditto starts to laugh, it weakens and can't hold its transformation.
Ditto is mentioned in Manaphy’s trophy description.
As a Poké Ball Pokémon
Ditto was confirmed in the August Nintendo Direct to appear as a Poké Ball Pokémon. When it appears, it will transform into a purple version of the summoning fighter, acting as a CPU player and taking their physical appearance, with the only difference being a purple gelatinous texture. Players and Assist Trophies alike can attack the clone. Ditto can be defeated, but doing so will not score a point. It is also the only Poké Ball Pokémon in the game who can be defeated. The AI for Ditto is considerably less skilled than a regular CPU, often standing still for periods of time and attempting individual attacks only, much like the behaviour of many other Poké Ball Pokémon. However, its attacks deal 1.1x regular damage to compensate.
While Ditto will exactly copy most characters exactly like how they are originally (minus the purple gelatinous texture), the following copies will be different:
If Spirits are enabled, Ditto will only have the primary spirit effects, but like other Poké Ball Pokémon, its stats are affected by the summoner's spirit team.
Ditto cannot be summoned during an 8-Player match.