Issac is a blue Popepi Pipepo who initially appears caged for sale at a market stall, later revealed as the shop's true owner with the shopkeeper as his apprentice. His age is inconsistently documented as either 1,000 or 5,000 years. Arrogant, wise, and scheming, he provides humor through smooth-talking salesmanship and deception, frequently showcasing skills in lying and negotiation.

His background includes multiple marriages, most recently to Jerusha—another Popepi Pipepo and his contentious ex-wife. Their encounters spark frequent arguments, yet Issac harbors unresolved feelings, recalling their time together as his happiest. He uses the nickname "Isaku" for her, which she weaponizes to irritate him. Though they persistently undermine each other, underlying affection lingers.

He joins Sheyenne Rainstorm and Dr. Kiel Aronnax’s group after overhearing Sheyenne mention a female Popepi Pipepo, hoping it might lead to Jerusha. Within the team, he offers comic relief and unexpected insight. His interactions emphasize cunning and opportunism, occasionally revealing sentimentality about Jerusha. His development focuses on enduring ties to Jerusha and integration into the group’s adventures.