Explain how Harper Lee uses Mrs. Dubose and Boo Radley to develop the theme that things aren't always what they seem in To Kill A Mockingbird?
Jem and Scout only see the one side of Mrs. Dubose in Harper Lee's To Kill a Mockingbird. Her tirades against them and her harsh words about Atticus seem to come from an old woman who hates all around her. But as Jem spends more time with her, he sees that her health is far from sound, and he seems to tolerate her on a slightly better level. Following her death, Atticus explains her morphine addiction to Jem, and tells him that she is one of the most courageous women he has known. When Jem is given her gift of the flower--the same as the plant he destroyed--he tearfully understands that he meant more to her than he had realized.
As far as Boo Radley goes, this is pretty clear. All the kids, and most of the people of the town in general, see Boo as some sort of a monster. They are afraid of him and they tell all these stories about how bad he is. Yet we come to find out that he is actually pretty kind and does nice things for the Finch kids.
Mrs. Dubose seems like she is just a nasty old woman. But we later find out that one of her problems is a drug addiction.
In these ways, each of these characters shows that things are not always as they seem.