Polonius stumbles.

Mark Lawson describes a famous Hamlet moment in a piece for The Guardian about theatre errors that aren't:

"Similar punishment for subtle acting was suffered by the late Michael Bryant, when he played Polonius in Richard Eyre's Hamlet at the National in 1989. Bryant's playing of the moment when the character loses the thread of his thoughts – "What was about to say? By the mass, I was about to say something …" – included such an authentically panicked chasm in the line that there was an audible gasp from the stalls. During the interval, I heard some people discussing their horror; his only consolation would be the confirmation that truly great acting must look spontaneous."

There are more similarities between theatre and circus than meets the eye. Do we like to think when an acrobat stumbles, it's for the first time, that they're in genuine danger, even though we subliminally know they've probably done it every night of their lives.