"Birthdays!" Aziraphale exclaimed suddenly. This was after several silent moments spent picking at their spinach salads, and it surprised Crowley so much the demon's sunglasses flew right off his face.
"Birthdays?" he inquired haltedly, clutching at his chest. Recovering from his flail, he contorted himself into his chair trying to rescue his shades from the terra-cotta stones of the bistro terrace.
"Birthdays," the angel agreed, holding up a radish speared on the tip of his fork. "We never thought of having any. You and me, I mean."
Crowley straightened in his chair and slipped the shades back on, squinting at his friend. He reached for the glass of Chianti warming next to his serviette and absently miracled it chilled before bringing it to his lips. "I don't think we're supposed to have birthdays. What with not having been born and all that."
Aziraphale chewed on the radish, waving his hand dismissively. "Doesn't matter. I think we owe it to ourselves to have an actual reason to celebrate, for once. Red socks in public laundrettes can only cut it so many times."
Crowley cackled, evidently pleased with himself. "But did you see their faces! Pink, the lot of them!" He could feel the points in his favour down below racking up like evil little marbles in a playground full of mean children. That lawyer had looked particularly fetching with a bright shade of salmon under his red face. Crowley had always thought he ought to get extra commendations when he managed to get steam to whistle out from people's ears. Let's see Hastur do that!
Aziraphale was now inspecting his radicchio with the air of someone who was coming up with something very important. Crowley held his breath inspite of himself. "We," decreed the angel, sitting back in his seat with resolve, "will from now on celebrate a birthday each, once a year. I declare mine to be April 28th."
"A fine date," Crowley approved, but failed to see the reason behind the choice. Aziraphale looked rather satisfied with himself as he impaled a cherry tomato. Satisfaction looked good on the angel, Crowley thought, then he banished the thought with mild horror. "Mine will be, um."
"Excellent!" Aziraphale cheered, reaching for his drink. He stopped mid-movement. "December 10th. That's today."
"Quite right," Crowley crowed, hiding his embarrassment at being found out with a more habitual smugness.
Aziraphale sipped his wine, eyes narrowing suspiciously at the demon. "And how do you propose we mark the occasion?"
Crowley had many ideas as to how they could do just that, but wisely voiced none of them. Instead, he blushed. "Er."
Aziraphale blinked, then smiled a deviously pointy grin Crowley would've been proud of under different circumstances. "Saaaay it."
Crowley started and clutched at his salad fork. "No!"
"What's the point of a birthday if you won't tell me what you want?"
"Because it's personal," Crowley objected with an edge of hysteria. He ignored Aziraphale's smirk. "And besides, what would your people say if you did that sort of thing with someone from our side?"
There was a pause, during which Crowley considered wishing into existence a very very large hole in the ground.
"Yes?" The 's' was uncharacterically short as he busied himself swallowing his own tongue.
"What kind of thing?"
Crowley thought it particularly cruel of Aziraphale to torture him this way, even though he had no idea how the angel (a being of pristine mind, Crowley would've liked to remind Aziraphale with a smack behind the head, one that would relocate the angel's own glasses fairly effectively) had the necessary information to take the piss.
Crowley blushed furiously and mumbled his answer into a conveniently refilled glass of Chianti.
Aziraphale dabbed at his mouth delicately with his folded serviette, hiding his own sneer. "Fine, don't tell me. Gives me plenty of time to plan for next year."
Crowley didn't know whether to hide or grin himself silly.