This should be easy for Trekkies and shouldn't be hard for me but I can't remember enough to even construct a search.
At the end of this Star Trek TOS episode Spock notes something to the effect that even the highest forms of intelligence need to "play" sometimes.
It provided insight into what took place during the episode.
I'd like to refer to this in order to excuse myself for spending too much time in Stack Exchange and not enough doing what I'm supposed to, but I'm not even smart enough to figure out what I'm remembering.
What exactly did Spock say, in what context, and about who?