When Doodle finally walks, Brother waltzed Aunt Nicey around the room for a brief, joyful moment. Look at the line. What happens to end their joyful dance? Symbolically, what is interesting about this supposedly light-hearted moment?

The waltz of the brother and Aunt Nicey foreshadows the future of the brother.
After Doodle demonstrates that he can walk, the family rejoices in Doodle's success, and Aunt Nicey dances with the brother. However, Aunt Nicey steps on the brother's toes with her heavy shoes, hurting him "so badly" that the brother feels he is "crippled for life." This reaction is a reminder of the attitude toward disabilities that prevails in this family that has kept little Doodle in a back room and built a casket for him when he was an infant in expectation of his death. When he does not die, the brother tries to force Doodle to learn to walk and not be "crippled" because he is embarrassed to have a brother who cannot walk.
After Doodle's death, the brother becomes crippled from the limitations of his heart and mind that would forcibly demand that Doodle act "normally." In his crippled state, much of the beauty in life seems to have disappeared for the brother. In the exposition of his narrative, for instance, he states that the bleeding tree is gone, and in its place stands a grindstone, often a symbol of continuous and monotonous hard labor. Now, he adds, "if an oriole sings in the elm, its song seems to die up in the leaves, a silvery dust." In other words, with the death of Doodle, the beauty in the brother's life has disappeared. He now is spiritually "crippled for life," limited in his ability to enjoy life and see beauty in it as did Doodle.