The Torah spoke about four sons: one wise, one wicked, one simple, and one who does not even know how to ask a question...
A sampling from the Four Sons in Hagaddot Illustrations from the 16th century to present times:
Immigrant Family — Chicago Hagaddah, 1879
Here the generation gap between East European immigrants to the U.S.A. and their assimilated wicked son is foremost. Having adopted new-fangled American ways, the son smokes, dresses in black clothes with a modish cut, and dances on his tilted chair. He takes the initiative in attacking his parents with an accusatory finger as if to say derisively, "What is this ritual for you?" The simple and the silent children, distinguished only by their hand motions, are mesmerized by the wicked son who sits at the head of the table holding forth. The other three figures — mother, bearded father, and wise child with kippah — are dressed traditionally in pale white. Their body language bespeaks paralysis, passivity, and lack of communication. The conversation is dominated by the three children in black, all with uncovered heads and backs turned. The family is divided culturally and generationally. Only the wise child identifies with the old ways.
The Four Children as Four Books: David Wander
The four children in The Haggadah in Memory of the Holocaust reflect different attitudes towards Jewish tradition as symbolized by a book, for we are "the people of the book," in the phrase coined by the Muslims. For the wise child, Judaism is an open book with letters to be read and studied. For the wicked child, the tradition burns up as it is destroyed. The association with Nazi book burning is chilling. For the simple child, the book is open since he asks questions, but the child himself is still blank, still unlearned. Finally, for the fourth child, Judaism is a closed book. This child awaits someone to "open" the book and the pupil to one another as the Haggadah advises "You will open up" the Exodus story for the child who does not even know how to ask.
(Text from Jewish Heritage Online Magazine)