Who is the "Model Boy" in The Adventures of Tom Sawyer (chapter 5)?
The so-called "Model Boy" is identified in this chapter as Willie Mufferson. Twain uses the capitalized epithet to signify the disdain in which his protagonist, Tom Sawyer, holds the unfortunate Willie, who is so good that all the other boys dislike him. He is called the "Model Boy" because he behaves exactly as parents wish their boys to behave. In this chapter, he can be seen escorting his mother to church, taking immense care of her as if she were fragile. Obviously, this excellent behavior on the part of Willie endears him greatly to not only his mother but also the other women in the church. The problem for the other boys is that, by comparison to Willie's "model" behavior, the others's poor behavior appears even worse—presumably Willie is held up to them as an exemplar of how they ought to behave, as suggested by the comment that he is "thrown up to them." Naturally, this causes the other boys to resent him. Tom is particularly disdainful of the fact that Willie carries a white handkerchief; he does not himself have a handkerchief and thinks they are a mark of "snobs."
On chapter 5 of The Adventures of Tom Sawyer "Model Boy" is identified as Willie Mufferson. The reason why he is referred to as Model Boy as if those were his name and last name respectively (which is why the nickname is capitalized), is because Tom absolutely loathes him for Willie being a good, respectful and seemingly loving boy whom everyone idolizes.
Willie, however, is indeed a sort of model boy. He would take his mother to church and take excessive care for her. Like the narrator explains, Model Boy was the favorite of all the other matrons. Also, which really annoyed Tom, Model Boy would wear a white handkerchief to go to church, and it hung quite naturally in his suit. To Tom, who did not own a handkerchief, felt jealous and deliberately felt that all boys who did own handkerchiefs were snobs.
Therefore, Model Boy was the antithesis of Tom, and that is why he detested him.