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Fun Fact: Aziraphale learned the dance Gavotte (this is mentioned in season one).
The final step of Gavotte is to kiss your partner. This explains why Aziraphale was upset when the Gavotte went out of fashion. I imagine he learnt it in the hopes that one day he might convince Crowley to dance it with him. But by the time he was brave enough to ask Crowley to come to the club, he couldn't because nobody danced it anymore.
Aziraphale had waited over a hundred years, waiting for the right opportunity, to ask Crowley to dance with him.