Why is it significant that George enters the scene while Walter and Beaneatha playfully enact African characters?

Beneatha dances to Nigerian music as she shows off her African garb, and sings in a Nigerian dialect. Walter walks into the apartment drunk but instinctively starts dancing, loving the beat of the drum in the music. During this scene, the inebriated Walter begins to act out a scene in which he is the chief of a tribe. George's arrival turns this playful episode into a tense commentary on African heritage and class. George, thoroughly confused, addresses Beneatha and asks her to change out of her "costume" and get ready for their theatre date. The interaction between Walter and George reveals the tension between the working and upper-middle classes.