carnival is officially opened when king momo, wearing the traditional costume for the occasion, is crowned on the friday of carnival.

in a televised event, the mayor of rio de janeiro hands over the key to the city, a huge gold key covered in glitter, and for the five days of carnival king momo symbolically runs rio de janeiro. 

one of the principal symbols of carnival, king momo is inspired by momos, the god of sarcasm and mockery in greek mythology, who lived a life of joy and humor and was expelled from mount olympus for ridiculing the other gods.

historians document that the role or symbol of king momo was first used in roman parties in the 4th or 5th centuries bc, where a fat and outgoing man would parade around decadent parties, signifying the rule of a period of complete freedom.