He took a series of very shallow breaths, and then said as quickly and as quietly as he could, ‘Door, if you can hear me, say so very, very quietly.’
Very, very quietly, the door murmured, ‘I can hear you.’
‘Good. Now, in a moment, I’m going to ask you to open. When you open do not want you to say that you enjoyed it, OK?’
‘ΟΚ.’
‘And I don’t want you to say to me that I have made a simple door very happy, or that it is your pleasure to open for me and your satisfaction to close again with the knowledge of a job well done, OK?’
‘ΟΚ.’
'And do not want you to ask me to have a nice day, understand?"
‘I understand.’
‘OK,’ said Zaphod, tensing himself, ‘open now.’
The door slid open quietly. Zaphod slipped quietly through. The door closed quietly behind him.
‘Is that the way you like it, Mr Beeblebrox?’ said the door out loud.
— Life, the Universe, and Everything
The door refused to open. It said, “Five cents, please.”
He searched his pockets. No more coins; nothing. “I’ll pay you tomorrow,” he told the door. Again he tried the knob. Again it remained locked tight. “What I pay you,” he informed it, “is in the nature of a gratuity; I don’t have to pay you.”
“I think otherwise,” the door said. “Look in the purchase contract you signed when you bought this conapt.”
In his desk drawer he found the contract; since signing it he had found it necessary to refer to the document many times. Sure enough; payment to his door for opening and shutting constituted a mandatory fee. Not a tip.
“You discover I’m right,” the door said. It sounded smug.
From the drawer beside the sink Joe Chip got a stainless steel knife; with it he began systematically to unscrew the bolt assembly of his apt’s money-gulping door.
“I’ll sue you,” the door said as the first screw fell out.
Joe Chip said, “I’ve never been sued by a door. But I guess I can live through it.”
— Ubik