Yep, I'm looking at the pages melf is talking about. There's a full page photo of an X-rayed tangle of rats.
The caption that goes with it reads:
The rat king was found in the winter of 1963 by a Dutch farmer in Rucphen, North Brabant, who heard loud squeals coming from a pile of bean sticks in a barn. Upon further investigation, he discovered a rat king consisting of seven adult blacks, five females and two males, all of similar age. The X-ray of the knot showed some fractures, with signs of callus formation, and there were also fractures in some vertebrae. This suggest that the tails had been knotted together for some time, perhaps originally becoming entangled when the animals had crowded together in a nest, and that the rats had tried desperately to free themselves.
Here's about as good of a pic of it as my webcam can capture.