In the news today, an 800-year-old Easter Egg: Giotto sneaked the Devil into a painting of St. Francis of Assissi. They speculate that he was annoyed with someone. Took some guts to do that, too. Disney may get very angry at little jokes in their movies but they haven’t yet burned someone at the stake for it.
See the full story from the International Business Times, who has the best big picture.
Detail below shows Mr. Beelzebub.