Summary: Inspired by the book's comments that, first, the beds (plural) in Crowley's flat are always made, and that, second, there is one (and only one) bedroom.
The beds in Crowley’s flat were always made -- with the single exception of when Crowley occasionally slept in one of them. There were two, decorating the single bedroom much the same way a vase of plastic flowers might be put out to “liven things up a bit.”
If there had been a second exception it would have had something to do with Aziraphale. It seemed, however, that the angel knew a trick for getting under the covers without mussing them in the slightest, which was probably the polite way for one’s body to intrude into the fabric’s simple world if one absolutely must.
Crowley always took great pleasure in intruding as rudely as possible.
They would occupy the twin beds on those occasions that they’d put in a good evening of drinking and didn’t quite feel like sobering up. Usually these nights fell on a Saturday, since Sunday was, after all, a day of rest. Crowley took the left; Aziraphale preferred the right.
This time, one of them was helping the other to a bed, and both of them thought they were doing the helping. (For Crowley, being helpful was acceptable on the grounds that sleeping in the next morning counted towards Sloth.) Sometime during this their left hands got tangled together, which they realized when they tried to part and couldn’t.
Crowley shrugged and waved the beds closer together. Aziraphale helped. The frames knocked together with a muffled thump.
“Do two twin beds,” Aziraphale wondered out loud, “make a queen bed?”
“Don’t even talk to me about Queen,” Crowley warned blearily, and flopped down on the left side. This had the effect of yanking the angel down after him, though onto his own side.
They both lay there for a moment, Aziraphale staring up at the ceiling thinking he should put on those very stylish tartan pajamas he’d brought. It would be a shame to waste them, anyway. And they were very comfortable. He knew they were, because he’d tried them on in the store, so it would be a shame not to...
“D’you have to think out loud?” Crowley interrupted, mumbling into his pillow. With his free hand, he made what might have been correctly interpreted as a vaguely rude gesture if Aziraphale had been looking, which he wasn’t. “There. Now jus’ be quiet, m’kay? Sleep.”
Aziraphale found that he was now wearing the pajamas. They were just as comfortable as he remembered... Though as far as he could recall, they hadn’t been quite that low cut in the store. He yawned, and sighed, “Really, m’dear...”
And then they were both asleep, their hands still clasped together.