From the "Restaurant at the End of the Universe" by Doug Adams ...
The quadruped Dish of the Day is an Ameglian Major Cow, a ruminant specifically bred to not only have the desire to be eaten, but to be capable of saying so quite clearly and distinctly. When asked if he would like to see the Dish of the Day, Zaphod replies, "We'll meet the meat." The Major Cow's quite vocal and emphatic desire to be consumed by Milliways' patrons is the most revolting thing that Arthur Dent has ever heard, and the Dish is nonplussed by a queasy Arthur's subsequent order of a green salad, since it knows "many vegetables that are very clear" on the point of not wanting to be eaten — which was part of the reason for the creation of the Ameglian Major Cow in the first place. After Zaphod orders four rare steaks, the Dish announces that it is nipping off to the kitchen to shoot itself. Though it states, "I'll be very humane," this does not comfort Arthur at all.
Several years later, the principal characters encounter a herd of Ameglian Major Cows on the planet Nano, a colony planet established for exceedingly rich refugees from the destroyed Earth. Ford and Arthur (who is now far more open-minded after years spent traversing the galaxy) seriously consider the Cows' offering themselves as a meal, only to be interrupted by the arrival of the Norse thunder god Thor and his subsequent duel with Bowerick Wowbagger. However, the lightning display accompanying Thor's arrival kills and chars several Major Cows (while their still-living herdmates curse their fellows' luck), and Ford and Arthur take the opportunity to sample the cooked meat. Later, a Major Cow is shown offering itself to Thor at the thunder god's victory party.
Hey, it could happen and good thing I've got my towel.