You, Crowley, and Aziraphale were in a polyamorous relationship. You were out in public and someone came up to you and started to flirt with you. The thing that you didn't know is that Crowley was watching you two. Crowley had never acted jealous the only time that could make Crowley jealous was when you were being romantic with Aziraphale but that never made Crowley jealous. But this random person flirting with you made Crowley's skin crawl. He was watching from afar jealousy rising in him.