It was not that Claudette discouraged familiarity; it was rather that she was in such control of her sexuality that she could channel it into her characters. Fredric March realized early in the Manslaughter shoot that Claudette had a rare combination of sensuality and propriety: “There was such a tremendous, smoldering sensuality to her, and that kind of chemistry usually would make the average woman a wanton, but Claudette had dignity and a sense of fitness of things."
For The Sign of the Cross casting was almost complete but DeMille lacked a Poppea, the empress-wife of Nero. He was aware of Claudette, a regular on the Paramount lot; she intrigued him with her banked-down sensuality that could flare up, enkindling a scene of intimacy and leaving a residue of embers when passion was spent. Poppea was really a supporting role (Claudette had a total of five scenes), but DeMille was determined to give her enough screen time to leave an impression. Claudette enjoyed playing the oversexed Poppea. The first time she appears on screen, she is luxuriating in a sunken pool of black marble supposedly filled with donkey’s milk, the empress’s favorite form of bathing.
“Everybody on the Paramount lot had a crush on her,” says producer A. C. Lyles, then an office boy. And once the public was treated to the titillating sight of an unclothed Colbert frolicking in a bath of ass’s milk, she attracted legions of new admirers. “Two men with cardboard stirred up the milk at the other end of the bathtub so it would make waves,” she disclosed to Rex Reed, “and the milk went below my nipples. DeMille would yell ‘Cut!’ till they got more milk above the censorship level. I was sweating like hell in all that hot milk!” DeMille, however, was forced to use the footage already shot when, after a dinner break, everyone returned to the set to find that the milk had cooled down and curdled into cheese.