No, seriously, that's the episode title. Spock's brain gets stolen. The rest is just dumb. But there is a theory that it's all better if you change "brain" to "dick".
The Enterprise Incident
Kirk and Spock play spy and Spock falls in love with a Romulan. Kirk tries on Vulcan ears. It's a good time.
The Paradise Syndrome
Kirk, Spock, and McCoy wonder how pine trees made it across the galaxy. Wow. What an amazing coincidence...