Marvin: "I am at a rough estimate thirty billion times more intelligent than you. Let me give you an example. Think of a number, any number."
Zem: "Er, five."
Marvin: "Wrong. You see?"

Arthur: "Marvin, any ideas?"
Marvin: "I have a million ideas. They all point to certain death."

"My capacity for happiness," he added, "you could fit into a matchbox without taking out the matches first"

"Simple. I got very bored and depressed, so I went and plugged myself in to its external computer feed. I talked to the computer at great length and explained my view of the Universe to it," said Marvin.
"And what happened?" pressed Ford.
"It committed suicide," said Marvin and stalked off back to the Heart of Gold.

"What's up?" [asked Ford.]
"I don't know," said Marvin, "I've never been there."

I could calculate your chance of survival, but you won't like it.

"I'd give you advice, but you wouldn't listen. No one ever does."

"[Trillian] is one of the least benightedly unintelligent life forms it has been my profound lack of pleasure not to be able to avoid meeting."

On being left in a parking lot for 500 million years: "The first ten million years were the worst. And the second ten million years, they were the worst too. The third ten million years I didn't enjoy at all. After that I went into sort of a decline"

"I ache, therefore I am."