What is Doodle's appearance?

Doodle, the narrator's younger brother, is evidently a rather strange-looking child, with odd proportions and generally quite sickly and unable, at first, to walk. Seven years younger than the narrator, the boy has a large head, with a small red and shriveled body which resembles that of an old man. This seems to have furthered the general supposition that he would die soon; when Doodle was still an infant, his parents had a coffin built for him. His real name was William Armstrong, but the narrator gave him the name "Doodle" because the way he crawled backwards on the hearth rug reminded him of a doodlebug.
Doodle was unable to walk until he was five years old. Until then, the narrator was tasked with pulling his brother around in a cart which had been specially built for the purpose. When Doodle was five, the narrator took it upon himself to teach his brother to walk.