The king is the central character in 'the king's magic drum story'. Besides, there could be characters such as a wizard who gives the king the magic drum or an enemy who tries to take the drum away from the king. There might also be the king's loyal subjects who are affected by the magic of the drum.
In the 'the king's magic drum story', the main character is the king who has the magic drum. There could be other important characters as well. For instance, there might be a wise old man who knows the secrets of the drum and guides the king on how to use it. There may also be a group of thieves who attempt to steal the drum for their own greedy purposes. And the king's court jester might play a role, perhaps being the first to notice the drum's strange powers and bringing it to the king's attention.