Star Trek 50th Anniversary Blogging: "Spock's Brain" (September 20, 1968)
And DeForest Kelley faces a similar problem. He goes from dead-pan seriousness to over-the-top bug-eyed, failing to modulate his performance effectively from scene to scene. One minute he’s asking (seriously) the (awful) question: “In the whole galaxy, where are you going to look for Spock’s brain?” with utter solemnity. And in the next he is marveling, wide-eyed, that a child could complete the brain surgery.