Lincoln tells Kirk, "There is no honorable way to kill, no gentle way to destroy. There is nothing good in war, except its ending." This speech, written by the Star Trek screen writers, has become so popular that some people mistakenly believe it to be something the real Abraham Lincoln said.
This is the final episode of the series to feature the entire ensemble cast of Kirk, Spock, McCoy, Scotty, Uhura, Sulu, and Chekov. This episode also marks the final appearance of Nichelle Nichols (Uhura) in the series.
"The Savage Curtain" introduces Klingon founding father Kahless and Vulcan founding father Surak to the Star Trek universe. Kahless' history played an important role in several episodes of Star Trek: The Next Generation (1987) and Star Trek: Deep Space Nine (1993) (where he is considered a force for good), and Surak's history was crucial to the final season of Star Trek: Enterprise (2001) which also gave a little bit of backstory to Colonel Phillip F. Green. Zora of Tiburon is the only "historic" figure introduced here who was not further developed in a later Star Trek series.
This marks the second time TOS encounters a silicon-based life form. The first time is in The Devil in the Dark (1967). Janos Prohaska played both lifeforms, with Bart La Rue supplying the Excalbian's voice.
Tiburon, homeland of the cruel scientist Zora, is named after the Spanish word for shark, and was also the homeland of Doctor Sevrin, the villain-of-the-week of The Way to Eden (1969).