Scene from Book 3 of "The Hitchhiker's Guide to the Galaxy": "Life the Universe and Everything"

Admittedly more colorful depiction than the description of the swamp on Sqornshellous Zeta, where the trees are said to be gray but at least I got the mist in. Marvin, the depressed robot has been stranded on this miserable planet in a swamp inhabited by mattresses that swim around and are ridiculously carefree. The mattresses are often captured and then killed and slept on as industry for the planet, but are cheerfully unaware of this fate. Marvin's damaged leg prevents him from leaving and this subjects him to meaningless banter with them on a daily basis as they never remember previous conversations with him.
=========================
"A mattress had just met a robot.
"Hello, robot," said the mattress. "Bleah," said the robot and continued what it was doing, which was walking round very slowly in a very tiny circle.
"Happy?" said the mattress.
The robot stopped and looked at the mattress. It looked at it quizzically.
It was clearly a very stupid mattress. It looked back at him with wide eyes...
"We could have a conversation," said the mattress. "Would you like that?"
"No," said Marvin.
"My name," said the mattress, "is Zem. We could discuss the weather a little."
Marvin paused again in his weary circular plod.
"The dew," he observed, "has clearly fallen with a particularly sickening thud this morning.".. (quotes from "Life, the Universe, and Everything" by Douglas Adams)==========================