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Jonathan Bailey thought he'd single-handedly ruined a highly anticipated show when he was a child ... violating a theater superstition right before a memorable bomb.

The actor opened up about his foolish faux pas during an episode of "Actors on Actors" -- the popular Variety series where stars interview one another about their lives and careers.

Bailey told Superman himself, David Corenswet , he took part in the 1996 show "Les Enfants du Paradis" helmed by "Four Wedding and A Funeral" actor Simon Callow ... and, before the show, Jonathan says he said the word "Macbeth."

If you don't know ... there's an old acting susperstition which prohibits actors from saying the play title "Macbeth" in a theater -- with allegedly dire consequences if they do.

In true ghostly fashion, t

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