The idea of the Phylosians was forced upon Walter Koenig by Gene Roddenberry, who wanted a race of talking plants in the animated series because it was not possible to do on the original Star Trek (1966). Koenig had to write ten to twelve drafts of the script before it was accepted by Roddenberry. According to Koenig, he was offered the chance to write additional scripts for the series; however, he turned it down because of Roddenberry's excessive and controlling demands for rewrites. As a result, this is the only episode involving him.
This features the one and only time in all of the Star Trek series and films that Captain Kirk says anything close to, "Beam me up, Scotty!" It has long been thought of as one of those made-up phrases connected to the franchise (in the original Star Trek (1966), Kirk and others always said something like "Scotty, three to beam up." or "Enterprise, beam us up."), but he does say "Beam *us* up, Scotty" here.
The Retlaw plant which attacks Lieutenant Sulu is named after Star Trek (1966) star Walter Koenig (first name spelled backwards), who scripted this episode; he also auditioned to lend his voice to the role of Keniclius, but was turned down. Koenig openly regrets that Filmation couldn't (or, according to himself, wouldn't) hire him alongside his fellow veteran Star Trek actors due to budgetary concerns. To this day, he bluntly charges the studio heads with sacrificing too much artistic talent in the name of reduced costs: "It's hard to believe what a bunch of tightwads (Lou Scheimer and Norm Prescott) were, if you've never worked with them...and even harder to describe, after you have."
First occasion where Spock receives a mind touch from another Vulcan.
Spock II is the third-largest being Spock ever mind melds with (unless the Lactrans from The Eye of the Beholder (1974) are equal or bigger). The cosmic cloud from One of Our Planets Is Missing (1973), and V'Ger from Star Trek: The Motion Picture (1979), are the largest.