When Dill comes to visit Maycomb the first summer, he is completely fascinated with the Radley house and the concept of Boo.  He starts teasing Jem about it, saying that Jem was "too scared to even put [his] big toe in the front yard."  Well, that leads Jem to defend his honor, and Dill makes an actual dare.  He dares Jem to "go up and touch the house."  Jem takes Dill up on the dare, and runs up to the house and quickly slaps it before running back.  So, that is one of the dares given in relation to the Radley house. This dare is the beginning of a long obsession that the kids have with the house, and they devise even more daring schemes as the summers pass, the last one to go peek in a window.  During that escapade, Jem loses his pants and they all have such a close call that it puts an end to their dares regarding the Radley house.