Gastly

Gastly is a Ghost/Poison-type Pokémon introduced during the first generation Pokémon games. It evolves into Haunter at level 25 and then into Gengar when traded. Gastly are mostly composed of poisonous gas, which surrounds what appears to be their main body.

In Super Smash Bros. for Nintendo 3DS, Gastly appears as an enemy in Smash Run. As it is engulfed in poison gas, it is immune to melee attacks and can only be taken out with projectiles. It can damage players on contact and will sometimes follow them.