By the end of his first summer with the Finch children, Dill (Charles Baker Harris) is obsessed with making Boo Radley come out.
When Dill first arrives, he makes the summer more interesting because the children act out stories from movies and books with three people. Dill is a good actor, and a good friend.
But by the end of August our repertoire was vapid from countless reproductions, and it was then that Dill gave us the idea of making Boo Radley come out. (ch 1)
The story of Boo Radley is way more interesting than any of the fictional stories they act out. The children divide their time between re-enacting the Radley saga and trying to pass notes to him or daring each other to go near his house.
"He'll probably come out after you when he sees you in the yard, then Scout'n' me'll jump on him and hold him down till we can tell him we ain't gonna hurt him." (ch 1)
It makes sense that Boo’s story would fascinate Dill. Fatherless and sent off to his aunt’s house each summer, he knows that it means to be a loner. He seems to identify with Boo’s plight, and sympathize with him. While it’s fun to make Boo the villain, there is also a certain amount of sympathy there.