Title is derived from a famous line in Shakespeare's play, Hamlet. Prince Hamlet is determined to prove that his mother the queen and her new husband murdered his father. To startle them into a guilty confession, he plans a play to be presented at the court, showing how they did it, and says: "The play's the thing wherein I'll catch the conscience of the king..."
When Crumb is reassuring his fellow actor that he needn't be so panicky about appearing in front of an audience, he tells him he's as good as Crumb's favorite actor John Wayne. Wayne's real name was Marion Morrison and Crumb shares Wayne's unusual first name - Marion.