And In This Fairy Tale It Was So (1984)

Once Koshchey the Immortal caught the Cat-Scientist and complained that he was bored and had no one to torment. In exchange for help, he promised to let the Cat go. The Cat, as such help, offered Koshchey to marry, but in order not to scare away the brides, he advised the villain to dress up as a good fellow. Despite such a cunning trick, Koshchey failed time after time.