Who is Karl from Welcome to the Monkey House and what is their importance?

Joe is a 6-year-old, black orphan living with nuns in a small village in Germany. It is not clear how he ended up there. Joe is told by another orphan, Peter, that his mother was a German woman and his father was an American soldier who left her. Peter says Joe is not a real German. Joe is sensitive, and this hurts his feelings. A nun reassures him that no one, not even Peter, knows who his parents are.

Joe is a lonely dreamer. During daily walks, he always wanders out of his place in line and ends up trailing behind the other orphans. He is physically quite small, and one of the sisters takes particular care of him. When he wanders to the end of the line each day, they talk. Joe is inquisitive and has lots of questions for the sister about America, his parents and many other things.