Mendez II was a mutant and one of the earliest progenitors of the Mendez Dynasty. Very little is known about this mutant, except for the fact that he was held in high regard, and was instrumental in the formation of the Doomsday cult that would evolve. A psalm attributed to Mendez II is included in the mutants' Doomsday prayer book, and a bust of him was constructed and placed upon a plinth within an air tunnel passageway outside of the mutant cathedral. 
Presumably, Mendez II was a biological descendant of the first Mendez who occupied the West Coast Forbidden Zone in the late 20th/early 21st century. It can also be assumed that Mendez' genealogical line extended into the 40th century, culminating with the Dynasty's final inheritor, Mendez XXVI. Whether or not Mendez was the mutant's true birth name, or merely an honorarium is unknown.
- Mendez II is referenced in Beneath the Planet of the Apes, but does not make an actual appearance.
- The first draft screenplay for the movie gave a brief physical description of Mendez II: "...a long white corridor lined on one side by head-and-shoulder portraits - each titled and dated... We start on an antique, cracked canvas in an old-fashioned gilded frame, labelled: Mendez I: 1997-B.3. The portrait is that of a handsome, strong-jawed, dark-haired, military-moustached soldier in the 20th century uniform of a U.S. Army five-star General. His likeness survives in the portrait of Mendez II - V, though the uniform has been replaced by clothes and (later) robes of an advancing fashion."
- The Beneath the Planet of the Apes novelization as well as the final shooting script by Paul Dehn indicates that all of the bronze busts featured in the cathedral's underground causeway were those of the entire Mendez family line.
- Planet of the Apes Revisited - First Draft Screenplay at Hunter's Planet of the Apes Scripts Archive