Idea I might write after indulging in some back and forth with a friend: rather than keep their Arrangement a secret from their superiors, Crowley tells hell that he’s trying to tempt the angel Aziraphale to fall, while Aziraphale convinces his that he’s experimenting with whether it’s possible to redeem a demon.
Since tempting an angel to Fall would be a crowning achievement for any demon, and since heaven is pretty willing to let Aziraphale have his experiments as long as he doesn’t interfere with their greater plans, they allow it, too.
Aziraphale and Crowley are both well aware that the other is supposed to be “tempting them” away from their side, and mostly just use the opportunity to spend as much time indulging in human pleasures as much as possible.
“I got him to do a round of temptations for me and he did a really good job,” Crowley tells Beelzebub, while at the same time Aziraphale is explaining to Gabriel how he convinced Crowley to do some of his miracles “for the sake of convenience” and Crowley added some touches Aziraphale wouldn’t have thought of.
Aziraphale produces a list as long as his arm about all the good Crowley has put into the world since his last check in. It’s completely accurate. Crowley talks about all the petty frivolities he gets Aziraphale to to indulge in, entirely honestly.
Neither heaven nor hell suspects, and they’re allowed to carry on their Arrangement without fear of repercussion as long as they make a play of tempting each other.
Jeez ain’t that accurate

incorrect-doctorwho
enby-distortion

