Hot Under the Collar.

Jerry tries to seduce his girlfriend Monica via hypnosis, but it accidentally makes her want to enter a convent and take a vow of chastity instead. Jerry tries to get her out by disguising himself as a priest and, later, a nun. Alas, his rescue attempt crosses paths with a mobster who's looking for his hidden stolen diamonds in the convent. Things get even more complicated when the pope himself decides to pay a surprise visit.