Disclaimer: Crowley and Aziraphale belong to Mr. Pratchett and Mr. Gaiman. How I Met Your Mother and everything associated with it belongs to Mr. Bays and Mr. Thomas (and probably some other people too). I own nothing and profit nothing.
How I Met My Angel - Episode 4, The Return of the Cufflinks
"Look, Crowley, there's something I have to say and there's no good way to say it, but we're both mature beings and I think that the truth is probably the best way. I don't think you're the one for me, my dear. I don't want to waste your time because I am terribly fond of you and I have the greatest respect for you, but this just doesn't seem right."
Crowley, who had until this point been enjoying dinner out with his friend of six thousand years, and boyfriend of three months, gaped at him. Aziraphale looked sheepish, and said, "I'm sorry."
"I'm not the one for you?" Crowley practically screeched. Heads began to turn in the restaurant, sensing the possibility of entertainment at the expense of someone elses discomfort.
Aziraphale tried to make placating gestures with his hands. They didn't work. "I did say I was sorry. I thought it would be the mature thing to do to tell you right away…"
Crowley's voice dropped to the pitch that indicated he was dangerously annoyed and considering jumping the border to furious. "It's the anniversary of my Fall."
Aziraphale winced and dithered. "Yes, I know I didn't realize that it was…it's just that we never talk about it and I can never remember…"
"It's the anniversary of my Fall and you know how depressed that makes me and now you're telling me I'm not the one for you?" It was barely a question, falling instead in the realm of the incredulous repetition that occurs immediately prior to a woman in a television sitcom humorously slapping the bumbling idiot who dared speak such foolishness to her.
Aziraphale, not having watched many television sitcoms, mistakenly tried to reason with him instead of responding with self-effacement. "Look, my dear, it really isn't that big a deal. I mean, look at the odds. It's like you lost the lottery."
Crowley continued to be furiously incredulous. "Are you trying to tell me that dating you is like winning the lottery?"
"No, no, no, that isn't what I meant," Aziraphale said, backpedalling with all his might.
"Alright," Crowley said, adjusting his glasses and allowing one moment of calm to wash over the table before he shouted, "So what's the problem?" while slamming his hands on the table and nearly upsetting their several glasses (and bottles) of wine. A murmur of appreciation for the emotion of the performance swept through the watching restaurant patrons.
Aziraphale winced again. "It's…I can't explain it."
"TRY!"
"It's…ineffable."
Heavy, angry silence fell. Even the other dinners felt it, and worried just a bit.
"Ineffable." Crowley deadpanned.
"Er…yes?" Aziraphale regretted his choice of words, but it was too late to retract it now.
"'Ineffable' is not trying to explain, Aziraphale. In case you haven't noticed, 'ineffable' is trying to pass off not having a clue. 'Ineffable' is not having the sense you were created with and pretending that was the Plan. 'In-bloody-effable' is why I can't get f-ed. 'Ineffable' is not why you are breaking up with me!" Crowley's voice had risen in volume during the tirade and now most of the restaurant was speculating on the fighting couple's sex life.
Aziraphale covered his face with his hands. This was not going as planned. "Oh, God, what's going on?" He groaned.
"Alright, maybe you need a little help. Here, what's going on is, we were friends for nearly six thousand years. Three years ago, you knew you were getting Recalled, and all you did was leave a message on my ansaphone. On the anniversary of my Fall. It took you three years to get back, and when you did, you tracked me down and asked me out on a date, and then decided to dump me for no reason three weeks later. Again on the anniversary of my Fall! That's what's going on, angel!" The patrons of the restaurant had begun to lose the thread of their entertainment and looked at each other quizzically.
"No, it's—it's not like that. I'm just—it's, it's, it's—" Aziraphale floundered.
"WHAT!" Crowley roared.
Channeling six thousand years worth of men who are really bad at break ups, Aziraphale responded, "I'm just, like, super busy right now."
There was a sound like a tea kettle right before it begins to boil. It was coming from Crowley. His eyes were glowing, and it could be seen even from behind his sunglasses. What followed was a fight of the sort that hadn't been seen since before the Arrangement. There was some shape-changing. Most of the patrons of that restaurant lived lives much more full of fear than previously.
Even after they patched things up, Crowley and Aziraphale couldn't set foot in that restaurant again. At least, not until after it got a new owner.