So last night I finally finished I Am Spock, Leonard Nimoy's second biography concerning the pointy eared Vulcan we all know and love, since i had finished i decided that the next book on my list was Star Trek Academy: Collision Course, the first of, what i hope to be a long, series of books by William Shatner about the days before TOS when our beloved characters are in Starfleet Academy. The book so far is pretty much amazing, and funny. It tells the story of the teenage Kirk and Spock, and how they met and ultimately became friends after they cross paths in a bar where Kirk gets them both arrested for stealing a starfleet car. While in custody for the theft, the two get a chance to talk, and during this talk the Spock fan learns something very interesting about they're green-blooded buddy.

At one point kirk refers to the authorities as "clowns". After this Shatner writes:

"To a Vulcan, the idea that a specific class of performers existed whose sole purpose was to elicit from their audience and intensely personal emotional response in public was repugnant, but to Spock, it was also strangely fascinating. He often wondered what his response to a clown might be. One possibility was that such an encounter might confirm his mastery of self-control, and he would not laugh. But another, more troubling possibility was that he would lose all Vulcan reason and his human half would rise unbound to the surface of his mind and shame him.
Spock frequently had nightmares in which he arrived at school and suddenly broke into laughter or tears, Though he could never discuss such a thing with his parents or his peers, since accompanying his parents to Earth, clowns had had become a constant source of concern for him."

In other words, even Spock is afraid of clowns, in a very logical way course.