In one of those that's-just-cool stories, the New York Times reports that Andrea del Verrocchio's sculpture of David had originally been intended to have Goliath's severed head behind David's left foot, but that wouldn't fit on the pedestal, so they sawed it off and jammed it in between the feet. "They" were presumably the city fathers of Florence, and they did it in around 1470. Or else it was the Medici, just before that. In fact, the whole thing is a supposition from examining the head in the course of restoration, but it seems to be pretty well-founded.
Why is this cool? Well, for me it's particularly cool because my first appreciation of art history (as opposed to just knowing what I like) was from a lecture about the various medieval and renaissance Davids; Verrocchio wasn't my favorite, Donatello was, with the goofy hat, the insouciant pose, and the bubble butt. Anyway, the lecture made me think for the first time about the way that art exists in history, and not just in a museum.
Secondly, it's cool because some of the things in the lecture turn out not to be true, and that means that knowledge is increasing. Our perceptions of the universe (though still and always incomplete) are just a trifle closer to the universe itself. And that's cool.
Thirdly, it's just a great story. "Damn, we've bought this sculpture to put on the pedestal, and now it won't fit. Do you think the Medici will give a refund?"
"Nah, let's just jam it on anyhow. How about this?"
"You can't leave the head hanging off like that, people will walk into it!"
"OK, the head will have to go."