Shadow Sneak is Greninja's side special move in its playable Super Smash Bros. appearances. In the core Pokémon games, Shadow Sneak is a Ghost-type move that Greninja can learn at level 23.
By holding down the special move button, a shadow is projected that moves forward in the direction it is facing. The shadow always moves a set distance, and Greninja can also move forward or backward slowly when projecting the shadow. After a while Greninja automatically warps to where the shadow is and attacks with a kick; this can also be done by releasing the special attack button. The shadow cannot move on slopes if Greninja is on flat ground.
In Super Smash Bros. for Nintendo 3DS and Super Smash Bros. for Wii U, the two variations of this move are Shadow Strike and Shadow Dash. When using Shadow Strike, the move takes longer to perform, but the shadow can move farther across the ground and the attack is more powerful. When using Shadow Dash, Greninja automatically warps a set distance and attacks; this is faster, but less powerful.