Caspay was a mutant who lived beneath the ruins of New York City in the latter half of the 40th century. He was a high-ranking member of the community, and possessed the ability to project his thoughts directly into the minds of others. Further, Caspay could pull abstract mental impressions from a target's mind and visually project them. Although he was more than capable of physically speaking, his evolved persona preferred communication through telepathy.
- In Paul Dehn's first treatment for the movie, much reference is made to the fact that Caspay is a dwarf, but on sceen he was average height. "We learn that he is Minister for External Affairs. He has great cranial development and an extra finger on each hand, of which he is endearingly vain. 'Like all New Yorkers, I am proud to be a Mutant.'" In the treatment he is the only mutant, other than Mendez XXVI, to be named, and seems to be his second-in-command.
- All of the mutant elders wore liturgical vestments, which were color-coordinated with the visual effects of their thought projection abilities. Caspay wore a turquoise (/green) stole over his tunic to match the color of his psychic impressions.
- Each Inquisitor pursued an individual line of questioning with Brent; Caspay probed for beliefs and opinions.
- Beneath the Planet of the Apes
- Beneath the Planet of the Apes (comic)
- Beneath the Planet of the Apes (novel)
- Planet of the Apes Magazine: Beneath the Planet of the Apes
- Adventures on the Planet of the Apes: Beneath the Planet of the Apes
- Conspiracy of the Planet of the Apes
- Death of the Planet of the Apes