Foo Fighters

Foo Fighters is a Stand appearing in Stone Ocean, notable for being a swarm of plankton that holds together as a single humanoid figure. It gains a personality and goes by the nickname F.F. Its look shifts over time: bare, it is a tall, dark, robotic form with an alien face, but it later keeps the shape of a dead inmate named Atroe, a woman of ordinary height and slim frame. As its sense of self deepens through time spent with Jolyne Cujoh, its true form drifts toward a more human appearance while still holding traces of the older figure.

Being a living colony rather than a normal body gives Foo Fighters a set of unusual traits. It has no limb to cripple and no vital spot to strike, so common attacks pass right through it, and only harming the entire colony can put it in danger. As a hive mind it can break itself into independent sub-bodies to fight several foes at once or move about unseen, and as long as a single organism survives with water present, the colony multiplies again and rebuilds itself. Given enough water it can even flood a room and strike with its own mass. Its glaring weakness is dryness: robbed of moisture, the plankton perish quickly, so it depends on a steady water supply. Unlike many Stands, ordinary people can see it.

It can also invade a human body, seizing control of that person's mind and memories and wearing their skin as a cover, which is how it came to impersonate Atroe. While hidden inside a host it no longer needs constant water and can even reshape or contort the body, but it grows less nimble and risks bleeding out and drying up that way. Beyond disguise, it can nudge water around with fine enough control to shape a small mirror from a fraction of a cup, fire clusters of plankton like a gun to pierce skin and invade another person, and pack wounds to keep someone from bleeding to death.

The Stand and its user are one and the same, the entity F.F. Originally set to a task by Enrico Pucci, it found a conscience and a self through its bond with Jolyne Cujoh and sided with the heroes. Its identity is fragile in a specific way: should the whole colony die and the Stand collapse back into a DISC, it would forget everything it learned and revert to a mindless Stand once fused with a fresh batch of plankton.