Spock: This is the new brig, Captain. It is escape-proof.
Kirk: How do you know?
Spock: The designers tested it using the most intelligent and resourceful person they could find. He failed to escape.
Kirk: This person didn't by any chance have pointed ears and an unerring capacity for getting his shipmates into trouble, did he?
Spock: He did have pointed ears.
Spock to Kirk explains that this new brig is completely escape-proof. To guarantee that, they used the most intelligent, most resourceful person they could find and was unable to escape. Kirk wonders to Spock if this person had pointed ears, and a propensity for getting his shipmates in trouble - meaning was it Spock. Spock simply responds that he did have pointed ears.