"I claim to be one of your old gods, who gave you instruction, and you dare to pretend that you do not know me?"
The Enterprise crew encounters an alien who claims to be one of Earth's old gods.
This episode provides examples of:
- Ancient Astronauts: Kukulkan explains to Kirk and his men that he came to Earth in the ancient past and inspired the primitive people to worship him, becoming the basis for the Mayan god of the same name, the Toltec god Quetzalcoatl, and the Chinese dragons.
- Beethoven Was an Alien Spy: Once again, the Enterprise meets an alien claiming to be a God of primitive Earth, this time the Aztec God Kukulkan.
- Bittersweet Ending: The crew are eventually able to reason with Kukulkan, but the alien decides to head off into deep space, likely to be alone for the rest of his life.
- Chekhov's Gun: When Dr. McCoy is teleported to Kukulkan's ship, he mentions that he has his medical kit with him. Near the end of the episode, a Capellan Power Cat has gotten loose; Captain Kirk uses a hypo from the kit to inject the Power Cat with a powerful sedative, ending the threat.
- Contrived Coincidence: Kukulkan is coming to Earth to wipe out the human race because he's angry that humanity hasn't contacted him. One of the officers on duty on the bridge is Ensign Walking Bear, who just happens to be an expert on ancient Earth cultures and recognizes the shape of Kukulkan's ship. Walking Bear says the name "Kukulkan", which not only prevents Kukulkan from destroying the Enterprise but convinces him to allow several Enterprise crew members to try to solve a puzzle. If they solve the puzzle, Kukulkan will give up his plan to destroy humanity. Ensign Walking Bear didn't appear in any previous or subsequent animated episodes, just this one. What are the odds?
- Did You Just Flip Off Cthulhu?: McCoy is not afraid to challenge Kukulkan when the powerful alien claims he can do whatever he wants to Kirk and crew.
- Feathered Serpent: Kukulkan is a giant snake-like being with wings and feathers who was the inspiration for the Mesoamerican legends of Kukulkan and Quetzalcoatl.
- Gilded Cage: The alien creatures Kukulkan keeps aboard his ship are shown telepathic visions of their ideal environments. Kirk and crew point out that they are all still technically being imprisoned.
- God Guise: The alien Kukulkan was considered a god by ancient humans, inspiring legends of serpent gods.
- The Great Serpent: Kukulkan is a very large snakelike fellow who inspired the civilizations of the Mayans, the Toltecs and the early Chinese.
- Last of His Kind: Kukulkan mentions that his entire race was wiped out while humans were still very primitive.
- Lotus-Eater Machine: The animals in Kukulcan's zoo believe that they are living in their natural environment, a hallucination generated by Kukulcan's machines.
- Obliviously Evil: Kukulkan essentially takes Kirk, McCoy, Scotty and Walking Bear hostage. He also fails to realize that locking animals in cages, even if they are "safe and contented" can be considered cruel.
- Wise Serpent: Kukulkan guided the early Mayans out of tribalism and into civilization and academia. He's pleased that his name and legacy are remembered, but still regards humans as childlike, inept and immature, still needing his guidance.
