When performed, Pichu will make a quick teleport-like action in any direction.
Inputting another direction during this first teleport allows Pichu to immediately perform a second teleport upon finishing the first. Pichu's Agility can be used in more directions than Pikachu's Quick Attack, and also travels slower and covers slightly less distance. Pichu will also be dealt 1% recoil damage for the first jump, and another 3% if it uses the second one. Agility does not deal any damage, meaning it is functionally more similar to Quick Attack as it appeared in Smash 64 as opposed to Melee. Pichu's up special has 1 frame of lag if the player hits the ground correctly, making it the most lagless move in Melee, but if the player messes up, he or she will have 14 frames of lag. The player can quickly jump and use the up special and then input another attack. For reference, look here or here for more details and tricks.
In Super Smash Bros. Ultimate, Agility once again serves as Pichu's up special. Unlike in Melee, the move travels farther than Pikachu's Quick Attack, and it deals less recoil damage to Pichu, though its continued lack of a damaging hitbox when combined with its retained recoil damage renders it entirely useless as an approach option compared to Quick Attack. As with Pikachu's Quick Attack, a red arrow now indicates the direction Pichu will go in during each part of the move.
In the Pokémon games, Agility is a status Psychic-type move introduced in Generation I. It increases a Pokémon's Speed stat by 2 stages. As the maximum amount of stat changes is six stages, the move can be used up to three times before any further uses will have no effect, going from doubling, to tripling, and then quadrupling a Pokémon's original speed stat value. Despite not being an Electric-type or damaging move in both Melee and the Pokemon series, Pichu still takes recoil damage when using it.
In the Pokémon games, Pichu cannot legitimately learn Agility, but its first evolution stage, Pikachu, can learn this move by leveling up in any game. This trait is shared with Skull Bash.