Bruno finding a friend, Shmuel.

When Bruno was exploring the back of his house, he found a boy who was on the other side of the fence. That boy was 8 years like Bruno. Bruno was so exiting with that because he needed to have a friend to play with. Bruno introduces himself, blissfully unaware of the situation on the other side of the fence. The Jewish boy's name is Shmuel. He was taken from his family and forced to work in Auschwitz. Almost every day, they meet at the same spot. Soon, they become best friends. Bruno and Shmuel even shared the same birthday. They are basically the same person born into different circumstances, one a Polish Jew, the other a German. 

I like this part very much, because Bruno finds a friend to play with and that friend, doesn't care if he was jewish, had the same years as Bruno and both of them born had the same birth. That was something that amazed me too much.