as for why this alternate ending has apparently never been performed again, it's not really a mystery. The scene has is not based on anything from the play and it has the Count behaving out of character for immediate gags, when in the rest of the show he's serious and intimidating; the entire thing is tonally inconsistent with the rest of the show. The real mystery is why it was created in the first place
if I had to hazard a guess, it's either some parody of some scandal that had actually recently happened or some sort of pop culture reference related to a famous role of one of the members of the principal cast
usually when some old work of fiction has something that seems completely random it's actually a reference to something well-known to the audience at the time it was made
usually
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