The second season kicks off with this notable episode (although "Catspaw" was the first episode of the season to be produced).
The second season introduces Walter Koenig as Helmsman Chekov, who makes his first on-screen appearance in this story. He was brought it partly to try and win younger viewers, with his look based upon 'The Monkees' (which started the same year as 'Star Trek'); and he was made Russian to reflect their position in the 1960s space race.
Also with the second season, DeForest Kelley's name is added to the main credits, reflecting how he had grown to be a key character over the first season of the show.
Anyway, the story itself. The episode is notable for our first glimpse of Vulcan, and many of their customs. It marks the first appearance of the Vulcan hand gesture (suggested by Leonard Nimoy), as well as the first on-screen uttering of "Live long... and prosper".
Many of 'Star Trek's episodes mirror human conditions, and this story can be dubbed 'Spock hits puberty'! He certainly acts like an angry teenager, throwing food offered to him at the wall, and shouting a lot.
This is one of 'Star Trek's most famous episodes, with the fight between Spock and Kirk being the most memorable scene. It has also been spoofed a lot, such as in the movie 'The Cable Guy' (1996), and in the second season 'Futurama' episode 'Why Must a Crustacean Fall In Love'.
The story is okay, and has some interesting details, but I confess to finding it a bit dragged out, and my attention did start to wander in places.
This is one of the most iconic episodes of Original 'Star Trek', but I wouldn't necessarily class it as one of the very best. It certainly has some good moments and some nice details, but I'm afraid there are many that I like better.