From the Super Mario Wiki
Wall-Luigi! is a Super Ability used by Waluigi in Mario Strikers Charged, and it briefly appears in the opening cinematic. In order to use this move, Waluigi has to earn his special item, which is depicted as his head. When the move is executed, Waluigi has increased speed and can create thorny purple vines behind him, which act as a wall. This wall blocks off other players, protecting Waluigi while he charges up his Mega Strike.