Star Trek: Asterisk "How Sharper Than a Serpent's Tooth"

Vital Information
Series: The Animated Series
Episode: S02E05
Air Date: October 5, 1974
Written by: Russel Bates and David Wise
Directed by: Hal Sutherland and Bill Reed

Kulkukan, the Mayan god, stops by for a visit in the Alpha Quadrant and takes Kirk and a landing party captive for a bit.

So, the Enterprise starts out pursuing a probe that came by the Alpha Quadrant to scan stuff and throw out some signals. It's the duty of the Federation to get in contact with other lifeforms, so, what the heck, why not?, let's follow the probe. Luckily, the plucky young Ensign Walking Bear is along for the ride in Sulu's place, so when they encounter a Mayan god, they just happen to have an expert with them to figure out what it is.

And encounter a Mayan god they do. Following the probe, they come across a ship that projects a holographic image around it of a serpent with wings. Walking Bear immediately recognizes this as Kulkukan. The ship attacks the Enterprise, but relents as soon as Walking Bear sees it. In the silence, Kirk tries to figure things out, but is cut short by the fact that random crew members keep disappearing. Including him! When all is said and done, Kirk, Scotty, Bones, and Ensign Walking Bear end up in a completely blank area with the voice of Kulkukan booming in their head.
And then Kulkukan throws a party! YEAH!
Kulkukan projects the image of an ancient city all around the crew. It looks familiar, but there are slight differences. With Walking Bear's help, Kirk figures it's an amalgamation of Mayan, Egyptian and other ancient cultures. And each one of these cultures were attempting to finish Kulkukan's design before he could return. The trouble is that none of them finished it. So, once the team figures that out, they finish the design and LO AND BEHOLD! KULKUKAN ARRIVES!

The serpent/bird creature explains that he was angry that humans seemed to have forgotten him, but was relieved when Walking Bear knew who he was. And now he can continue caring for the humans as if they were his children... except... wait... they're not children anymore. Kirk objects to being treated like children and then they find out they were basically in the Matrix along with a load of other animals.
Like this thing... the Green Rebo.
Some stuff happens and basically the crew uses the captive animals to attack Kulkukan and teach him a lesson that children eventually grow up. They don't need gods anymore. They have starships. And SCIENCE!

Overall Thoughts
The idea that ancient gods were actually aliens isn't new, it wasn't even new when this first aired. They've already encountered Apollo. In fact, come to think of it, this is basically just a Mayan repeat of "Who Mourns for Adonais?" Regardless, this time they were able to throw in a bit more creativity with character design and such because of the drawing and stuff. Again, great story mired by an awkward format.