"Ye-es," says Aziraphale slowly, eyes widening imperceptibly as he follows the coiling motion of the tail through his peripheral vision. He finds that he's sitting a little more stiffly in anticipation of something, some inevitable manner of mischief that is sure to follow. He fidgets a little, thoroughly provoked.

Any enquiries about Crowley's intentions would be much too obvious now; Crowley needs no further goading and Aziraphale isn't keen to give it at this point, nor does he particularly feel like playing hard to get. He comes up short, instead looking mutely at his companion with an expression that says some variation on I suppose you're quite pleased with yourself.