Foo Fighter is a stand and a stand user aswell, Inside a host, Foo Fighters can shoot small parts of itself as if it was using a gun (this is later shown to incorporate pistol parts into its hand). The bits of plankton colony can invade someone's body and take control of it. The shots have enough strength to pierce through skin. The plankton can help seal wounds, preventing someone from bleeding out and potentially saving them from dying. FF had developed her stand from a stand disc.