Who is moortje in the book anne frank?

There is no character named "Moortje" in Anne Frank's diary or the play "The Diary of Anne Frank."

It's possible you're thinking of a different character or have misremembered the name.

Could you please provide more information about who you're referring to? For example, what kind of character are you thinking of (a person, animal, object)? Do you remember any details about their role in the story?