Clark is a middle-aged African American man with short black hair, a thick beard, dark brown eyes, and noticeable wrinkles on his forehead. His usual dress consists of a white undershirt, denim pants, and a plaid jacket. Clark is characterized as the struggling owner of Cap'n Clark's Ottoman Empire. During an entire-store sale there, he discovers a maze of endless spaces on the other side of his basement wall, which he immediately obsesses over, given the fact that he’s a failed architect. This decision could possibly be a window into his mind at the time, during which his entire store was on sale with the tagline "Everything must go!", likely implying that Cap'n Clark's would soon close permanently, which may also explain why he seeks therapy. Although it is later implied that he only goes to therapy to validate himself instead of actually trying to change for the better. This is because he believes he is incapable of change, saying it’s “just the way (he’s) wired”. Clark's mental health slowly deteriorates over time, obsessively staying in and trying to understand the Backrooms. This is also where his worst traits, such as his rage, resentment, and avoidance of accountability, fully come to fruition. Following the distancing from Barbara (his ex-wife), he becomes withdrawn, depressed, and heavily dependent on alcohol, often using excuses and denial to avoid confronting the consequences of his actions. Despite these shortcomings, Clark is also extremely intelligent, resourceful, and genuinely passionate about discovering the truth behind the Backrooms. Once he realizes the significance of his discovery, he becomes obsessively driven to understand it, even when doing so puts himself and others in danger. He also craves validation and connection. His insistence on proving the existence of the Backrooms stems not only from scientific curiosity but also from a need to be believed and taken seriously during a period when much of his life feels out of control. Additionally, it's possible that Clark is obsessed with them because he denies his own reality, his life. Therefore, he lives in the Backrooms outside normal reality, where many things, like people, are misremembered. However, he gradually turns insane in these rooms. From Clark’s worst traits, the violent Pirate Clark was created. Clark was kicked out of his own house for breaking a glass and starting a angry argument with his wife.

Pirate Clark resembles Clark in his commercial pirate outfit but is malformed and significantly taller, at a height of roughly 7'7" to 8 feet. The outfit it wears consists of a teal-turquoise long-sleeve button-up with large collars, a long beige vest of sorts on top, a black belt over it, and over that belt is a purplish sash alongside dark brown pants. On the right leg is a white crew-high sock and a brown Oxford shoe. On the left leg, an amber wooden peg leg is jointed and resembles a furniture chair leg. Due to some error made by the Backrooms, its left shoe is fused to its lower back. Both of its hands have eight fingers. Its left hand has four brass red-gem rings, and its right hand has three brass blue-gem rings. On its head is a tricorne pirate hat and two feathers. Its right eye is elevated about half an inch (1.27 cm) from its left and noticeably bulges—the right having no eyebrow. Additionally, its left eye is duplicated slightly to the right. Its nose is bent and duplicated three times to his right. Inside its mouth, it has two tongues and rows of bottom teeth. It is also seen to have some kind of internal circulatory and cardiovascular system, given that it begins to bleed due to being bludgeoned by a rock shard during the film's climax (unlike the other Still Lifes, whom Clark took a piece out of to show an edible stuffing-like substance). In one of the final scenes of Backrooms. Pirate Clark is a physical copy of Clark, the troubled store owner. Pirate Clark comes across as aggressive and violent, much like Clark himself. Clark was the only one who managed to survive. This might suggest that both Clark and Pirate Clark were selfish, and that Pirate Clark chose not to harm Clark because of this similarity. Can’t talk.