Parts of France celebrated what was called the Feast of Fools between the 12th and 15th centuries. On New Year's Day, status was inverted among the clergy, in which lower-ranked monks and students wold become the bosses of the priestly administration. It was a way to elevate the lower ranks, if only for a day. Over time, the celebrations became rowdier, although they probably weren't as dangerous as the powers-that-be made them out to be. However, the idea spread from the church to the public, because it seemed so much fun. By the time the Feast of Fools was banned, it was getting some panicky criticism.
“Priests and clerks may be seen wearing masks and monstrous visages at the hours of office,” the theologians recounted, presumably with a sniff of horror. “They dance in the choir dressed as women, panders or minstrels. They sing wanton songs. They eat black puddings… while the celebrant is saying mass. They play at dice… They run and leap through the church, without a blush at their own shame.”
Now, that sounds like a party. Read more about the Feast of Fools at Atlas Obscura. ]