The New York Post said the rodent made its entrance while the actors were in the middle of a hotel scene in the comedy Tuesday.
As audience members chuckled at the unbilled performer's arrival, Bartha improvised, "This hotel has mice," which prompted Shalhoub to pick up a prop phone and complain to the faux hotel's front desk, the Post said.
The actors reportedly resumed their scripted lines without missing a beat as the mouse left the stage.
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