Functioning as a counterattack, Greninja strikes a pose and, when attacked, disappears in a puff of smoke with a wooden log or a Substitute doll taking its place; it then reappears with a strong flying kick. The log or doll can be hit and flung around by damage, and can even stop one-hit projectiles such as Shadow Ball or Charge Shot, or activate hitbox-detecting attacks like Upperdash Arm and Quick Draw, making it a situational shield. It disappears after a few seconds.
This move is functionally similar to Lucario's Double Team as a counterattack; however, a direction can be held after a successful counter to perform the countering attack in that direction. The counterattack can be directed in eight directions, including diagonally. If aimed downwards, the counterattack will meteor smash, although Greninja will likely self-destruct if this is done offstage.
While the counterattack itself is flexible, the counter itself is rather limited due to its average counter frames, rather slow startup, and high ending lag. Additionally, Greninja is not intangible during the kick, hence the attack can get interrupted by quick attacks such as a jab infinite, or even backfire with Greninja hurling straight into an enemy's powerful move.
However, in Ultimate, Substitute is more consistent as it slows down opponents and it now grants Greninja invincibility, making it more safe.
Special Move customization was added in Super Smash Bros. 4. These are the variations:
In Smash Tour
The Substitute Doll appears as a green trophy item: if a tour item targets the player who used it, the effect will be redirected to another random player. This also applies to exclude the player who used it from the effect of items that target all players.
The Substitute Doll trophy is available in Super Smash Bros. for Wii U, obtained by scoring 90 or more KOs in Solo Endless Smash while playing as Meta Knight.
Substitute is a Normal-type status move in the Pokémon games introduced in Generation I. When used, the Pokémon loses 25% of its maximum HP from its current HP and leaves the screen, replaced by a substitute doll. The substitute has its own HP which is equal to the HP the user lost to create the substitute, but derives its type and stats from the currently active Pokémon - the move Baton Pass allows for switching Pokémon without losing the substitute. When the Pokémon is attacked by any move that isn't sound-based, the substitute takes damage instead - a substitute loses all of its HP, it fades away. When the Substitute user wants to use another move, the Substitute and Pokémon will temporarily switch places to allow said Pokémon to use the move. If the Pokémon does not have enough HP to make the substitute, the move will fail.
While the move is widely available to almost all Pokémon via TM or Move Tutor, Greninja is one of the few Pokémon able to learn this move by leveling up as well. Its usage in Smash is a reference to the substitution/body-replacement techniques used by ninja in popular folklore to escape danger. The log occasionally left behind is a notable hallmark of this.