Problem V: Where's Waldo?

What's Wrong With This Painting?

Background: Hieronymus Bosch painted this center panel of a triptych on or about 1504. The triptych depicts the history of the world and progression of sin. The center panel, The Garden of Earthly Delights depicted here, illustrates a world deeply engaged in sinful pleasures. Someone made a mistake here in an attempt to hide another famous icon of the 1500's. Typical of the sort of challenge we see, what is that mistake?