Appearance
Crowley's wings were not beautiful by any stretch of the imagination. They had been at one point. They'd been a vibrant white, like all other angels, but of course falling changed everything. Now his wings were a stained yellow colour. It was as if some kind of animal with a bladder infection had peed on them. Aziraphale always commented that they kind of matched his eyes. Crowley always made sure to keep them in the best of shape, a little bit of vanity was always good to have for a demon. He rarely took them out though; most other demons had black wings which made Crowley stand out like a sore thumb. He had never met another demon with wings similar to his.
Sometimes when it was just the two of them Aziraphale forgot himself and would let his wings out. They were pure white and gave off an ambient glow; they were your uniform angel wings. Unfortunately Aziraphale had no time for taking care of them, so the 'heavenly glow' was ruined by astray feathers sticking out at all angles. Occasionally when Aziraphale would wander around the store they would trail around behind him, like two large dead birds that had been welded to his back. Sometimes on the longer nights as Aziraphale would pause in front of a bookshelf, forgetting his current task, Crowley would slip over and run his hands through the wings, straightening any astray feathers. After the first few times it had happened Aziraphale had gotten used to it. His automatic reaction was no longer to flee, but instead to relax and allow Crowley to straighten out the mess of fluff attached to his back.
Flying
Aziraphale was clumsy on his wings. He had been using them for millennia and yet he still couldn't quite get the hang of them. He would waver while in the air and sometimes they would decide to go back into his back altogether. He had discorporated once or twice on the account of misbehaving wings. Crowley loved to tease him about it, "An angel who can't control his wings? They might as well just clip them!" Aziraphale would simply roll his eyes and ignore the comment. He had tried for years to get the appendages to behave, but they simply wouldn't. They had a mind of their own.
Crowley was as graceful as a dancer. When he was in the air he moved with purpose and grace, not that he had Grace anymore. He loved the feeling of freeing his wings and just allowing himself to go free and glide over a town or a rural area. He had, jokingly of course, offered lessons on flying to Aziraphale. Aziraphale had politely, if not a little sarcastically, declined. Being in the air for Crowley was like being in the water for the ducks they fed each morning, it was just natural. Crowley had never had to take the time to learn to control his wings. They had listened to him for as long as he could remember.
Kiss
Wings had always been great indicators of emotion for angels and demons alike. They needed to be calmed and trained enough that they could be tucked away while on earth, and even then angels and demons had to be careful not to feel strong emotions. All training and reminders went out the window when their lips had first connected. Aziraphale could only thank his father that he hadn't been wearing a shirt he had particularly liked at the time, because it now had two vertical tears down the back. It had really been inevitable, or so Crowley said. They had spent millennia forced together in different situations, eventually hate turned to comradery, which turned to friendship, which turned to something... something else. The decades leading up to the kiss had been filled with all kinds of tension, they had the looming Apocalypse that couldn't and they were both being pressured by their respective leaders. It hadn't been passionate like the fires of hell, but it hadn't been chaste like the clouds in heaven. It had been like them, a dangerous mix of both. It had happened in the book shop, it was about a week after the Apocal-whoopsnevermind. They had both had a lazy day of doing nothing but enjoying the other's company. Neither would admit to initiating it, but in truth it had been Crowley. Crowley had been sitting behind the little counter while Aziraphale trundled around the shop rearranging books, he had moved over to grab something from behind the counter. Leaning over him Aziraphale had glanced down at Crowley and given him a disapproving look, "You could have grabbed it for me." That's when it had happened. Crowley had moved his face in and locked his lips to Aziraphale's, standing as he did so. Aziraphale had almost stepped back in surprise, that was when his wings burst out, stretching out in surprise right behind him. Crowley's had followed suit only seconds later, but his stretched forwards, almost reaching towards Aziraphale's. Aziraphale had relaxed into it and they had both picked up a rhythm, finally they both stepped back, "Or you could get it yourself." Crowley had remarked before attacking Aziraphale's lips again, allowing his wings to lazily rest around the two of them.
Defense
In the early days of their 'New' Arrangement Aziraphale had constantly worried that they were going to get in trouble for 'Fraternizing' with the enemy. Crowley would throw back that mutual orgasm was no reason to be in trouble. From there they usually ended up in an argument, or in bed. Their relationship wasn't perfect but it worked, and eventually Aziraphale's worries came to life. For Aziraphale they sent a, as Crowley would call them, 'mail order Angel'. They were glorified postmen. It was a warning from up above, it was along the lines of, 'While He accepts love and relationships of all kinds there is to be no fraternizing with the enemy. You are to cease your relationship of sorts with the Demon or consequences will arise' and with that the angel had left. Crowley's warning had been much more informal, if you could even call it a warning. An old friend of his had come up and said, "So they wanted me to let you know that they love the angle you're going for here, seducing an angel? Perfect. But don't y'know, get too attached. Just in case it doesn't work or something." His friend had picked up a bit of human slang and had hung out trying it out. In Aziraphale's bookshop. With Aziraphale standing right there. When the 'friend' was finally gone Aziraphale had sent Crowley a look, "High school reunions had better not be like this." Crowley had laughed at Aziraphale's statement before going over to peck him on the lips, "C'mon, angel. I have 'seducing' to be done." But that hadn't been the end of it. Slowly Aziraphale's warnings started coming in hundreds a week and the angels were of higher rank each month. Meanwhile hell had started to pick up on the fact that this meant a little more to Crowley than just some mere seduction. His superiors started coming to him more often. And it all ended up culminating on one day. It was about five months since the kiss that had taken place in the dusty bookshop. The Metatron himself had come for Aziraphale. He had simply given Aziraphale a firm talking to, and after a short discussion Aziraphale was free. No one cared about Aziraphale up there anymore. They weren't going to be watching from this point on. It really broke Aziraphale. He was still an angel, but none of his accomplishments would ever mean anything again. Crowley had been comforting him when Beelzebub had come for Crowley. Crowley had stepped out from behind the counter and looked at Beelzebub with a sneer painting his face, "You've finally come for me." He had spat. Beelzebub had been holding a dagger, "You're no longer useful Crowley. Your time has finally come." Crowley had adjusted his shades and stared right into Beelzebub, "Right." Crowley blinked. There was a white wing reached out in front of him, a flash of metal alerted him to the knife stuck into it. Beelzebub was gone. Crowley turned to find Aziraphale standing right behind him, his wings wrapped tightly around Crowley. The next few minutes were a blur to both of them. Crowley was yelling and trying to perform first-aid. Aziraphale was trying to calm Crowley, refusing to apologize for saving Crowley, "I'm barely an angel my dear." Aziraphale had coughed out, "I don't really have much left, except you. I wasn't just going to let them take that away."
Funeral
It turns out that once an angel dies its wings materialize. And stay materialized. The funeral had to be private for such reasons. It also turned out that wings were a vital organ for angels, even half angels. There weren't many others at the funeral. Crowley allowed his wings freedom for the event, as an homage.
A/N My first bit of Good Omens work, so I apologize for any mistakes or OOC bits. I hope you all enjoyed it! Feel free to review!