Toto, sometimes called Cassius in adaptations, is a black panther appearing across Jungle Emperor Leo iterations. His characterization shifts with each medium.

In the original manga, Toto acts as a comic relief sidekick to the lion antagonist Bubu (Claw), marked by pronounced cowardice. He frequently voices fear that Bubu might injure him during clashes with Kimba/Leo, often keeping physical distance to avoid harm.

Later anime adaptations, including the 1966 and 1993 series dubs, portray Toto as more sinister and calculating. He serves as the strategic counterpart to Claw's brute strength, willing to commit murder without remorse. Toto maintains criminal connections within the jungle hierarchy and treats subordinates like the hyenas Tom and Tab with open contempt, leveraging their fear while cautiously avoiding excessive provocation of Claw. This version also appears as a recurring villain in the 1989 anime reboot.

A distinct portrayal occurs in the *Onward, Leo!* series (episode 17, "Devil Falls"), where he is named "Slikar." Here, Toto operates independently, surviving by hunting weaker animals. After escaping a human trap, he reveals the humans intended to sacrifice him at Devil Falls. Though given food by Leo's cubs Rune and Rukio, he attempts to prey upon them, revealing his self-serving nature.

The 2009 film *The Brave Can Change the Future* reimagines Toto as a tragic figure. He is the last surviving panther, genetically engineered by humans and deemed a "failed product." This iteration becomes a semi-antagonist driven by profound existential despair and unresolved rage toward humanity. His final act involves confronting Leo and Ken'ichi while questioning if animal suffering impacted human consciousness. His closing monologue — "I wasn’t meant to live in this world anyway... This… is my way of leaving my mark" — underscores his fatalistic worldview and search for meaning before his implied demise.

Physically, Toto is consistently depicted as a lean, long-bodied black panther across all appearances.