The waiter approached.

"Would you like to see the menu?" he said, "or would you like meet the Dish of the Day?"

"Huh?" said Ford.

"Huh?" said Arthur.

"Huh?" said Trillian.

"That's cool," said Zaphod, "we'll meet the meat."

...

A large dairy animal approached Zaphod Beeblebrox's table, a large fat meaty quadruped of the bovine type with large watery eyes, small horns and what might almost have been an ingratiating smile on its lips.

"Good evening," it lowed and sat back heavily on its haunches, "I am the main Dish of the Day. May I interest you in the parts of my body?"

It harrumphed and gurgled a bit, wriggled its hind quarters in to a more comfortable position and gazed peacefully at them.

Its gaze was met by looks of startled bewilderment from Arthur and Trillian, a resigned shrug from Ford Prefect and naked hunger from Zaphod Beeblebrox.

"Something off the shoulder perhaps?" suggested the animal, "braised in a white wine sauce?"

"Er, your shoulder?" said Arthur in a horrified whisper.

"But naturally my shoulder, sir," mooed the animal contentedly, "nobody else's is mine to offer."

Zaphod leapt to his feet and started prodding and feeling the animal's shoulder appreciatively.

"Or the rump is very good," murmured the animal. "I've been exercising it and eating plenty of grain, so there's a lot of good meat there."

It gave a mellow grunt, gurgled again and started to chew the cud. It swallowed the cud again.

"Or a casserole of me perhaps?" it added.

"You mean this animal actually wants us to eat it?" whispered Trillian to Ford.

"Me?" said Ford, with a glazed look in his eyes, "I don't mean anything."

"That's absolutely horrible," exclaimed Arthur, "the most revolting thing I've ever heard."

"What's the problem Earthman?" said Zaphod, now transferring his attention to the animal's enormous rump.

"I just don't want to eat an animal that's standing there inviting me to," said Arthur, "It's heartless."

"Better than eating an animal that doesn't want to be eaten," said Zaphod.

"That's not the point," Arthur protested. Then he thought about it for a moment. "Alright," he said, "maybe it is the point. I don't care, I'm not going to think about it now. I'll just... er [...] I think I'll just have a green salad," he muttered.

"May I urge you to consider my liver?" asked the animal, "it must be very rich and tender by now, I've been force-feeding myself for months."

"A green salad," said Arthur emphatically.

"A green salad?" said the animal, rolling his eyes disapprovingly at Arthur.

"Are you going to tell me," said Arthur, "that I shouldn't have green salad?"

"Well," said the animal, "I know many vegetables that are very clear on that point. Which is why it was eventually decided to cut through the whole tangled problem and breed an animal that actually wanted to be eaten and was capable of saying so clearly and distinctly. And here I am."

It managed a very slight bow.

"Glass of water please," said Arthur.

"Look," said Zaphod, "we want to eat, we don't want to make a meal of the issues. Four rare stakes please, and hurry. We haven't eaten in five hundred and seventy-six thousand million years."

The animal staggered to its feet. It gave a mellow gurgle. "A very wise choice, sir, if I may say so. Very good," it said, "I'll just nip off and shoot myself."

He turned and gave a friendly wink to Arthur. "Don't worry, sir," he said, "I'll be very humane."

There are various different vegan philosophies, some basically won't consume anything that had anything they view as animal exploitation anywhere in the process

For example, to some of the more extreme forms of veganism, if your vegetables, grains, or other plant-based foodstuffs were hauled in a cart by a horse, or if you used an ox to pull a plow in the fields while it was growing, they wouldn't consider that to be vegan.

Some also object to honey for similar reasons.

Many, probably most, vegans don't go quite that far, but they're definitely out there, and everyone draws the line at a different place.

That's one variety of veganism, but hardly the only reason to go vegan.