The Death of Catherine the Great
Catherine the Great was a great woman, but also an incredible sexual deviant. She would have sex with anything that was even vaguely the right shape. In 1796, she even paid her staff to construct a special giant swing so that she could sit in the "lap" of her favorite stallion (a horse) and do the nasty with it! But I guess she didn't pay the construction people enough because the structure collapsed and Catherine the Great was crushed by her equine lover, becoming Catherine the Flat.
A subsequent medical examination revealed that she was pregnant, but details of the fetus' apparent parentage have been sealed by royal order for all eternity.
Behind the Legend
On November 5, 1796, Catherine the Great was checking on her staff when, in a tragic accident, a clotheshorse fell on her. The legend took off from there, spurred on by the fact that Catherine was sleeping with everyone.