Explaining Wyatt to himself

Yesterday Wyatt and I were looking at some pictures that arrived in the mail and Wyatt kept pointing everyone he knew, except he kept saying a weird word for himself. After about 20 pictures of Wyatt, I figured out that he was saying "you." Seemed weird to me, at first. Then I flipped through a couple more pictures and came across another one of him, and asked him who it was. When he didn't answer me, I said, "It's you." To witch he then replied, "you." So, my question is, how do I explain explain to him that "you" is the same as himself?