Near the beginning of "The Scarlet Ibis," the narrator and older brother of Doodle introduces him as "the craziest brother a boy ever had." Doodle appears

all head, with a tiny body that was red and shriveled like an old man's. Everybody thought he was going to die.

As others discussed below, Brother (as Doodle calls him) considers his younger brother to be crazy because of the boy's mental and physical disabilities. Interestingly, Brother also labels Doodle as crazy because Doodle develops and performs tasks backward.

Like F. Scott Fitzgerald's Benjamin Button, Doodle seems to age in reverse. As described above, he resembles an elderly man at birth. Although babies typically have large heads and are red at birth, their bodies tend to be smooth and unwrinkled. Doodle's wrinkled, withered body already looks like he is ready to die from old age. His parents even prepare for his death soon after his birth:

Daddy had the carpenter build a little coffin, and when he was three months old, Mama and Daddy named him William Armstrong. Such a name sounds good only on a tombstone.

Doodle's somber and unchildlike name of "William Armstrong" is ironic (after all, he is not strong). It is not appropriate for his personality but suited more to be printed on a gravestone.

When Doodle moves, he goes only in reverse. Brother says,

When he crawled on the rug, he crawled backward, as if he were in reverse and couldn't change gears.

Doodle cannot move forward physically and metaphorically; his development is arrested and he is never able to join peers at school.

Finally, Brother find Doodle crazy because Doodle is extremely sensitive; the boy appreciates and is touched by "the beauty of Old Woman Swamp" to the point of crying spontaneously. He also feels so mournful of the dead red ibis that he buries it.