"I mean, d'you know what eternity is? There's this big mountain, see, a mile high, at the end of the universe, and once every thousand years there's … - Neil Gaiman

"I mean, d'you know what eternity is? There's this big mountain, see, a mile high, at the end of the universe, and once every thousand years there's this little bird-"
-"What little bird?" said Aziraphale suspiciously.
-"This little bird I'm talking about. And every thousand years-"
-"The same bird every thousand years?"
-Crowley hesitated. "Yeah," he said.
-"Bloody ancient bird, then."
-"Okay. And every thousand years this bird flies-"
-"-limps-"
-"-flies all the way to this mountain and sharpens its beak-"
-"Hold on. You can't do that. Between here and the end of the universe there's loads of-" The angel waved a hand expansively, if a little unsteadily. "Loads of buggerall, dear boy."
-"But it gets there anyway," Crowley persevered.
-"How?"
-"It doesn't matter!"
-"It could use a space ship," said the angel.
Crowley subsided a bit. "Yeah," he said. "If you like. Anyway, this bird-"
-"Only it is the end of the universe we're talking about," said Aziraphale. "So it'd have to be one of those space ships where your descendants are the ones who get out at the other end. You have to tell your descendants, you say, When you get to the Mountain, you've got to-" He hesitated. "What have
they got to do?"
-"Sharpen its beak on the mountain," said Crowley. "And then it flies back-"
-"-in the space ship-"
-"And after a thousand years it goes and does it all again," said Crowley quickly.

There was a moment of drunken silence.

-"Seems a lot of effort just to sharpen a beak," mused Aziraphale.
-"Listen," said Crowley urgently, "the point is that when the bird has worn the mountain down to nothing, right, then-"

Aziraphale opened his mouth. Crowley just knew he was going to make some point about the relative hardness of birds' beaks and granite mountains, and plunged on quickly.

-"-then you still won't have finished watching The Sound of Music."

Aziraphale froze.

-"And you'll enjoy it," Crowley said relentlessly. "You really will."
-"My dear boy-"
-"You won't have a choice."