The Court Jester (1955) on Netflix

The throne of rightful king of England, the small babe with the purple pimpernel birthmark, has been usurped by the evil King Roderick. Only the Black Fox can restore the true king to the throne--and all he needs is the king's key to a secret tunnel. And while he's trying to steal it, someone has to change the king's diapers. The task falls to Hawkins, the gentlest member of the Fox's band. The Fox's lieutenant, Maid Jean, guards Hawkins and the babe while they travel, but when they meet the King's new jester on the road, they decide to initiate a daring plan for Hawkins to replace him, become an intimate at the court, and steal the key. So, humble Hawkins becomes Giacomo: the king of jesters and jester to the king. But things begin to get zany when the King's daughter falls for Giacomo, the King falls for Jean, people randomly sing what are supposed to be recognition codes, and a witch with very effective spells (and poison pellets) begins to interfere.