Early Talosians were much different
When the original pilot episode for Star Trek: The Original Series was in the planning stage, series creator Gene Roddenberry had something else different in mind from the short aliens with the large, pulsing heads. His idea? He wanted these cerebral beings to resemble crabs, though his reasoning remains a mystery.
When considering Roddenberry’s request, the production staff, according to Star Trek 365 The Original Series by Paula M. Block with Terry J. Erdmann, realized that aliens that looked like crabs would come across like something from a 1950’s horror movie, which was the very thing Roddenberry was trying to avoid. On top of that, creating such creatures would take an exorbitant amount of money from an already small budget.
The Talosians didn’t make it as crabs but other aliens did
The Talosians ended up being humanoid with small actresses, and their dialogue was dubbed by male actors. A renowned sculptor, Wah Chang created the aliens’ oversized heads out of foam and placed rubber bladder “veins” beneath the latex covering their heads. Using hidden tubes, he connected the bladders to squeeze bulbs that were held just off camera. Whenever the Talosians were communicating, someone would pump the bulbs, and it gave the image of pulsing neural activity. And they didn’t look at all like something from a 1950’s horror movie.
However, there are crab-like aliens that did make it to the television screen, and not only are they straight out of horror movies, they’re the stuff of nightmares. Dr. Who brought the Kantrofarri (or Dream Crabs) to life—telepathic creatures that feasted on humanoid brain matter while keeping their victims comatose. I don’t think any Whovian can forget the Christmas special “Last Christmas” where the Doctor and Clara arrived at the North Pole base to find the crabs chowing down on some of the infirmary’s team. Definitely too horrific for Star Trek standards.
The Talosians might be considered a bit simplistic now, but back in 1966, they made the perfect aliens for the brand-new sci-fi series. And even though they ended up not being used in the second pilot, they did debut in episodes eleven and twelve of the first season, (The Menagerie I&II). The two-part episode remains a fan favorite, and it went on to win a Hugo Award for Best Dramatic Presentation.