The user launches them self headfirst. It is similar in appearance to Luigi's Green Missile, only without the chance of a misfire and neither Pikachu nor Pichu can hold the charge infinitely, although in Melee and SSB4, Green Missile cannot be held infinitely either. The move can be charged up to increase the damage and range of the attack. In Pikachu's case, an uncharged Skull Bash deals 8% damage, while a fully charged one can deal up to 29%. Pichu's Skull Bash can be charged for longer, thus traveling further and dealing more damage and knockback, but hurts itself upon releasing (1%); when fully charged, the distance and knockback are tremendous, dealing almost 40% (close to a one-hit KO) and nearly covering the length of Final Destination. Pichu's Skull Bash is used in most Home-Run Contest strategies in lieu of the Home-Run Bat.
In Brawl, Skull Bash charges much faster than in Melee, and is an excellent move to recover with as Pikachu does not enter a helpless state after using it in mid-air. When fully charged, Pikachu will go about as far as the size of Final Destination. Even with its great distance, it's not used too often as Pikachu falls at a quick speed and the move itself is predictable, making the high landing lag all the more punishable.
Performing this move like a smash attack causes it to finish charging sooner.
Special Move customization was added in Super Smash Bros. 4. These are the variations:
Skull Bash is based on a move with the same name in the Pokémon games. It is a physical Normal-type attack introduced in Generation I. In the games, Skull Bash is a two-turn attack. On the first turn, the Pokémon using the move tucks its head in to prepare the attack and raise its Defense stat by one stage. On the second turn, the Pokémon launches forward to ram the foe with its head. The attack is very powerful, however, its two-turn nature makes it somewhat inefficient. The move's Defense-boosting capability on its first turn was not introduced in the Pokémon games until Generation II. This effect was never present in its Smash appearances.
Although Skull Bash was never an Electric-type attack, in Super Smash Bros. Melee however, both Pichu's and Pikachu's Skull Bashes have electrical properties. This was fixed in Super Smash Bros. Brawl, in which Pikachu's Skull Bash has a neutral effect. It also produces a small explosion behind Pikachu when used, similar to the explosive animation used for Skull Bash in the Pokémon games.
The move was available to Pikachu only by using TM40 in Generation I. It can, however, still have the move in Generation II games (the generation Melee was closest to), as they allow to trade Pokémon from Generation I games. Between Generation III and Generation VI, the move is unavailable for Pikachu to learn; as of Generation VII however, Pikachu can have Skull Bash if it is transferred from one of the Generation I games on the Virtual Console. Pichu, on the other hand, has never been able to learn Skull Bash in the games.