The Warming Pan Baby@Everything2.com:
The Warming Pan Baby: James [II Stuart] was disliked for a variety of reasons, the most notable is that he was Catholic.... English people were devoutly of the English Church, which itself was a form of Protestantism.... James II openly broke active laws like Test Act and appointed Catholics to positions in the military, the Universities of Caimbridge and Oxford, and government positions too. Not to mention the 7 Bishops case.... James II had two daughters from his first wife, both of whom were Protestant. However, James II... remarried... a Catholic princess.... On June 10, 1688, James's new wife, Mary of Modena gave birth to a son, James Francis Edward Stuart.
This did not bode well for the followers of the Church of England.... [I]t now looked like a Catholic dynasty was emerging.... What did ensue was perhaps the most scathing and vicious lie ever devised by the slanderous mouth of mankind. The rumor was that the baby, little Jimmy Frankie Eddie Stu, was not James II's, nor his wife's. It stated that the baby, while it was a boy, died in childbirth and that James II had "acquired" a substitute child.... During the middle ages... aristocrats often had the kitchen in a different building.... The food, after it was cooked, was placed into... warming pans... sent up to the dining hall. The baby was said to have been smuggled into the castle under one of the many warming pans brought to the King for dinner.
This was a lie, a rumor. Completely 100% not true. !True. False, etc...
Yet a remarkable number of somewhat-normal people believed it, at thetime.