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?"

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

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

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

"I've seen it. It's rubbish." About a Magrathean sunset that Arthur finds magnificent.

"Not that anyone cares what I say, but the Restaurant is on the other end of the universe"

"[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."

"Here I am, brain the size of a planet and they ask me to take you down to the bridge. Call that job satisfaction? 'Cos I don't."

Oh man, I just shot Marvin in the face.

Why didn't you say something, Marvin? Slipped your mind? You forgot to mention someone's in the bathroom with a goddamn handcannon?!?