During the December festival of Saturnalia, Romans threw their social norms out the window. They partied, gave gifts, ate, drank and gambled. They also engaged in role reversals in which masters served food to their slaves and the slaves could disregard their masters.
According to Wikipedia, "Romans of citizen status normally went about bare-headed, but for the Saturnalia donned the pileus, the conical felt cap that was the usual mark of a freedman. Slaves were not ordinarily entitled to wear the pileus, but they wore it as well. Everyone was "pileated" without distinction."
Just like this woodpecker.
(photo by Dick Martin)