Foo Fighters, more commonly referred to as F.F., is a major ally featured in Stone Ocean. F.F. is a mix of Stand and Stand User; A colony of plankton that is organized, maintained by, and essentially equivalent to the Stand, Foo Fighters. At first serving Enrico Pucci/Whitesnake, they soon ally themself with Jolyne Cujoh out of gratitude for being spared. F.F. can change their appearance at any time. However, their habitual appearance is that of the prisoner Atroe, a woman of average height and slim build with hair or a cap covering her head in a mop or bob forming a serrated edge at its ends. As their body is composed of plankton, F.F. can contort into impossible curves and even slip through barred fences unharmed. The bodies that they can form into are their sub-body, which they take the form of when initially fighting Jolyne and Ermes, and the main body, which they take the form of outside the water and when they have collected enough plankton. The bodies they have taken over were the three unnamed prisoners, including Atroe. F.F. is commonly shown carrying a 32 oz. cup near themself when they are not near a water source. In their Stand form, Foo Fighters takes two main appearances. Naked, a tall, dark, robotic humanoid of masculine proportions, and an alien visage. As F.F.'s identity develops due to their experiences with Jolyne, the true form of their Stand takes on a more human appearance starting to resemble the body they took over while still retaining some of the features of its older form. Foo Fighters is originally portrayed as an obedient minion whose sole purpose was to fulfill Pucci's orders. After meeting Jolyne, they begin to grow a sense of individuality throughout the story. Foo Fighters' personality hinges on the fact that they possess "intellect" but little life experience. During their introductory arc, their only goal is to preserve themself which includes obeying Whitesnake's instructions to guard the discs. As their guardian, they attack people very ruthlessly and aims to kill anyone approaching the disc's hiding place, regardless of their threat level. Being an intellectual being, Foo Fighters places great importance in themself and will implore their enemy to recognize them as sentient by calling them by their name. They also quote the astronomer Fred Hoyle to claim an "intellect" is guiding the universe, even predating it, all to say that even plankton can be intelligent. When Foo Fighters dies, Jolyne meets their ghost for a short time and the former mass of plankton happily contemplates their spirit form that confirms that they were truly alive and sentient. However, when Jolyne shows mercy toward them and saves them from dehydration, Foo Fighters discovers another way of thinking and grows interested in her, pledging to protect Jolyne and accompany her from now on disguised as the prisoner Atroe. Foo Fighters was shown not to have much of an eye for detail prior to meeting Jolyne Cujoh and Ermes Costello and laments their existence upon expecting death after being defeated by the two. When Jolyne saves them, however, F.F. immediately begins to notice more details around themself and comes to perceive the world around them as being more colorful. As a result of experiencing this whole new environment, they become extremely curious about everything around them, constantly asking questions to people and experimenting with the world, for instance, trying to do the contrary of what Atroe would have done. While they get along with other people, they have the strongest affinity for Jolyne for giving them freedom and "intellect", of which losing is their greatest fear. Foo Fighters eventually comes to accumulate enough positive memories of their companions that it comes to value them over their own safety, eventually sacrificing themself to close Anasui's wound with its plankton. Indirectly saving Jotaro and Anasui's, Foo Fighters departs satisfied to be able to salute Jolyne one last time before ascending to heaven. Because of their great dependency on water, Foo Fighters is obsessed with it and goes to great lengths to constantly hydrate itself. They carry a cup of water and will fight anyone over it, as well as drink any liquid as long as it contains water, be it blood or spit. Being a mass of plankton with no experience of society, they aren't disturbed by any of it.