"The Scarlet Ibis" contains many themes. Let's say a good theme to consider in relating it to Doodle is obstacles. Throughout the story, the character of Doodle wows his audience at home as he makes it past 3 months, eventually learns to crawl and finally learns to walk. He, like the ibis that is found far from his home, is a minor miracle walking about.
Doodle's brother overcomes some obstacles of his own. He begins to believe that in order for childhood to be fulfilling, he needs a partner in crime. Despite his brother's shortcomings, he commits to help him rise above these and often does so in secret.
Doodle is characterized as a weak figure from the beginning, all wrinkled and situated with a doctor who says he shouldn't live long. As time goes on and the brother builds skills in him, he is able to rise further than anticipated although this doesn't come without trial or significant effort.