The French call the sharp and witty retort, l'esprit de l'escalier, which means 'the wit of the staircase'. Yvette Guilbert was a past master at this, apparently.
She attended Marguerite Charpentier's salon, frequented by the wealthy and the famous. One of these grand ladies recognized her. According to The Private Lives of the Impressionists by Sue Roe, this grand lady exclaimed: 'My dear...I bet you don't remember me. We used to meet often a long time ago, before you became a star, when you were still a little seamstress.'
'Of course I remember,' replied Guilbert. 'I'll never forget how difficult it was to get you to pay your bills.'