I suppose I’m fortunate to be British. In those circumstances, the usual reply over here is “As the actress said to the bishop.”. An utterance bizarre enough to for a pre-schooler to ignore as grown-up nonsense.
That said, my son, who was a ruthless questioner of flat statements from the time he could talk, was also an excellent listener, with mixed results. At the age of ten or so, he was bombarding an unfortunate teacher with questions about a comment she had made. The harassed young woman then pointed out that it was just something she’d heard, and that “I didn’t expect the Spanish Inquisition!” To which my son dismissively commented “Nobody expects the Spanish Inquisition!” and carried on with his questions. Needless to say, Parents’ Evening that term was awkward!