Méndez was Kolp's First Lieutenant in Battle for the Planet of the Apes. He disagreed with Kolp's militaristic ways. In scenes deleted from the original release of the film, when Kolp went to battle with Ape City (made up of apes and humans who fled the Forbidden City before the war) with his mutant army, Méndez remained behind, supervising the team who safeguarded their "secret weapon"; the Alpha-Omega Bomb. Kolp ordered Alma to fire the missile if he were to be defeated. She promised to, but when Kolp lost the battle, and the default order to fire the missile at Ape City was received, Méndez instead rejected the order and dissuaded her from destroying the world, reminding everyone that using the missile would not just destroy the apes. Instead he suggested that if they venerated the fearsome object and preserved the missile through time, they would never lose hope or a sense of purpose. He became the new human (mutant) leader, and his attitude toward the missile became the code of the underground humans, who built their society to reflect that code. His successors in turn carried his name, as a reminder of their purpose. Completing the circle, in the second movie the leader of the mutants was also called Mendez and the implication is that those mutants, who worshiped that same bomb, were the descendants of this Méndez, who spoke so reverently about the bomb's power.
- The short story The King Is Dead - Long Live the King, written by Rich Handley for the anthology Planet of the Apes: Tales from the Forbidden Zone, gives Mendez a first name: Oscar.
- The scenes with the Alpha-Omega bomb were filmed to suggest a full-circle for the series of Apes films, with the descendants of Mendez continuing to revere the bomb up to the time of Taylor's arrival. However, these scenes were removed from the final theatrical cut. The scenes were restored for TV broadcasts in 1975, but did not receive an official release until included on a Japanese Laserdisc (in the early ‘90s) and on North American-region DVDs in 2006.
- Marvel Comics prequel to Battle, Quest for the Planet of the Apes showed Alma, Méndez and Governor Breck as slaves in the new Ape City who rebelled and escaped back to the radioactive ruined city. Marvel's Battle adaptation which followed had Breck as the lead villain rather than Kolp, as it was based on early scripts which still included Breck, before the role was recast.
- MR Comics' Revolution on the Planet of the Apes had Alma and Méndez as members of Kolp's elite team to rescue Governor Breck from his ape captors.
- The early story outline of Battle (as 'Epic of the Planet of the Apes') described Mendez as an electronics expert and Breck's Communications Officer.
- The later treatments for Battle described Mendez as Kolp's first lieutenant "who will one day be the first in the mutant dynasty that ends with Mendez XXVI in 'Beneath'", while Alma was now his Communications Officer.
- Paul Dehn's first treatment for Beneath the Planet of the Apes gave the first description of Mendez I - long before it was planned for him to be shown on film. Mendez rising from his throne... enters a long corridor, lined with statues... the names and dates on the plinths tell us that they are Mendez's ancestors: Mendez XXV, Mendez XXIV, XXIII, XXII, XXI etc. As Mendez walks, we are so to speak moving back in time; and as the dates become earlier, each statue's appearance approximates closer to the human norm... We end on Mendez I - a normal, handsome, strong-jawed, military-moustached, grizzle-haired soldier in the 20th century uniform of a five-star US General. The date: 1997 - B.3. In front of this, Mendez pauses for a moment... and whispers in a sort of agony: "Forefather, why can we not all look like you?" This shocks us, because it is directly contrary to his public teaching that all Mutants are beautiful.
- The earliest draft story outline for the fifth movie, dated 5 July 1972 and titled The Battle for the Planet of the Apes, was also written by Paul Dehn and revisited his earlier description. It was clearly intended to bring the saga full-circle and set up the events of Beneath. On the thirteenth anniversary of 'The Night of Fires', 90% of mankind is under ape control, with only pockets of human resistance in the North. Nimrod ("a grizzled giant by John Wayne out of Royal Dano" according to the outline), dressed in the battered uniform of a US Army General, leads this resistance and his forces are heading south in their makeshift convoy to finish the war against the apes. Nimrod greets a mutant human leader and tells him that his real name is General Mendez (a footnote says "we met Mendez XXVII in Apes II" (sic)). It was the later outlines mentioned above, written by John William Corrington & Joyce Hooper Corrington, which relegated Mendez to the role of a subordinate of Breck/Kolp.
- Battle for the Planet of the Apes
- Battle for the Planet of the Apes (novel)
- Planet of the Apes Magazine: Quest for the Planet of the Apes
- Planet of the Apes Magazine: Battle for the Planet of the Apes
- Revolution on the Planet of the Apes