The Madonna with Saint Giovannino is a painting that is reputed to have been painted by Domenico Ghirlandaio, although I have only seen that claim made on wiki sites.
It depicts the Virgin Mary looking down at a child that is being held by a cherub. In the upper right corner of the painting, there is a dark object in the air, and below that object there is a human figure that seems to be looking up at it.
This painting has been seized upon by UFO theorists as evidence that there were UFO sightings hundreds of years ago that fit the modern template. I'm not convinced; this seems like a case of modern people imprinting their beliefs onto the past.
That being said, I am curious what art historians have to say about this painting. Is there some theory about what that part of the painting is meant to represent?