Leonard 'Bones' McCoy: You know, back home we have a saying: "If you wanna ride in the Kentucky Derby, you don't leave your prized stallion in the stable."
Spock: A curious metaphor, doctor, as a stallion must first be broken before it can reach its potential.
Reference: Imdb Star Trek Quotes
I, however, was not able to find reference of this saying other than in the Star Trek context. Can they do that? Just make up sayings in the movie? :O