First appearance of the Vulcan hand salute. Leonard Nimoy improvised this symbol during the production of "Amok Time," modified from a traditional Jewish religious hand gesture.
First appearance of the Vulcan phrases "Peace and long life" and "Live long and prosper." Also the first ever Star Trek episode to feature any Vulcan characters other than Spock.
This is the only episode in the entire series to be set on the planet Vulcan.
Season 2 introduced new opening credits. DeForest Kelley's name was added to the "starring" cast and the theme music was extended and had the female soprano voice Loulie Jean Norman and percussion added to it.
Romulan helmets are reused from Balance of Terror (1966), this time worn by Vulcans during the pon farr ritual. In both productions, the helmets were a de facto economy measure as they precluded the need for the actors to wear ear prostheses.