In this famous “Mouth of Truth” scene, Gregory Peck ad-libbed the joke where he pretends his hand gets bitten off in the mouth of the stone carving. He borrowed the gag from Red Skelton. Before shooting Peck told the director that he was going to do the gag but did not tell Audrey Hepburn. When Peck pulled his arm out of the stone carving’s mouth with his hand pulled up his sleeve, Hepburn’s horror and surprise was genuine. She gave what she later recalled was “a good and proper scream,” and the scene was finished in one take.(x)
The “Mouth of Truth” or “Bocca delle Veritas” actually has a really cool story behind it. Men in the ancient world, when they believed their wives were being unfaithful, would drag them down to the mouth of truth, push their hand inside the mouth and ask them if they were having an affair. If they lied the Mouth of Truth would bite off their hand and expose their infidelity. The reason the hand no longer works is because one woman learned of her husband’s plan to bring her to the mouth of truth and ran to her lover begging him to take her away. Her lover calmed her down, told her he had a plan, and sent her back home. Sure enough, the woman’s husband came home that day yelling that she had been unfaithful and dragged her down to the mouth of truth. Just before he could push her hand inside it’s mouth the woman’s lover burst from the crowd, snatched her up and kissed her in front of everyone. Her husband angrily pulled her away, pushed her hand into the mouth of truth and demanded she tell him if she had ever kissed another man. The woman responded that aside from that madman just moments ago she had been faithful. Because she technically told the truth, the Mouth of Truth did not bite her hand but because it was so angry at having been thwarted, it refused to ever work again.