Julius was a gorilla charged with security at the Research Complex for studying captive humans. Like most of his species, he despised humans and felt they existed as nothing more than lower order animals, although he seemed less brutal towards the humans than the soldiers. He developed a particular dislike for the captured astronaut George Taylor who had been confined to a cage after suffering injury during a hunt. Julius delighted in tormenting Taylor and chastised him, calling the talking human a "freak", while washing him down with a high-powered water hose. He reluctantly aided Doctor Zira in her attempts to communicate with Taylor. A short time later, Doctor Zira's nephew Lucius helped Taylor to escape custody. He distracted Julius, edging him near the bars of the cage, enabling Taylor to grab him from behind. Lucius then struck Julius with a blunt object, rendering him unconscious (Taylor twice beat up Julius when escaping his cell). Although Julius doubtlessly survived the assault, he could not escape the fate that befell all of Earth's inhabitants only a short time later when his former prisoner, George Taylor, destroyed the planet by launching the Alpha-Omega Bomb.
In BOOM! Studios' Exile on the Planet of the Apes and Planet of the Apes: Cataclysm, Julius makes a brief appearance in the years before Taylor's arrival, again employed in a human research facility, working alongside Prisca and Servicus. He also appears briefly in the 2011 novel Conspiracy of the Planet of the Apes and its 2018 sequel Death of the Planet of the Apes, set during the time of Taylor's adventures.
- Buck Kartalian also played Frank, another gorilla in Conquest of the Planet of the Apes.
- Both his and Caesar's names are derived from Julius Caesar, a Roman emperor.
- One draft script by Michael Wilson had the character of Julius as a baboon.
- Planet of the Apes
- Planet of the Apes (Power Records)
- Planet of the Apes Magazine: Planet of the Apes
- Adventures on the Planet of the Apes: Planet of the Apes
- Conspiracy of the Planet of the Apes
- Exile on the Planet of the Apes
- Planet of the Apes: Cataclysm
- Death of the Planet of the Apes