In 'A Christmas Carol', Scrooge is initially a cold - hearted, greedy man who doesn't care about Christmas or others. The three ghosts are there to transform him. The Ghost of Christmas Past shows him his memories, the Ghost of Christmas Present shows him the current joys of Christmas around him, and the Ghost of Christmas Yet to Come shows him a possible dark future if he doesn't change. The carolers bring the Christmas spirit to the streets and into people's homes with their songs.
Mary and Joseph's role was to be the earthly parents of Jesus. They had to travel to Bethlehem where Jesus was born. The shepherds were messengers in a way. After seeing the angels and hearing the news of Jesus' birth, they spread the word. The Magi were important as they recognized the significance of Jesus' birth and brought valuable gifts, which also symbolized different aspects of Jesus' future role, like gold for kingship, frankincense for his divinity, and myrrh for his sacrifice.