Routine?

Usually, our afternoon routine is that I pick Isaac up from school and then we go to get Caleb. On Thursdays though, Isaac has therapy from 2 to 4. Today, when we got to Caleb's school to pick him up, Bryce kept asking where Isaac was (nevermind he went with me to drop him off at therapy!!). I kept telling him he was at therapy and he finally quit asking. He got quiet for a few minutes and then he started saying something in an argueing voice. I turned the radio off so I could hear what he was saying, then tried to hide my urge to die laughing. This is his conversation - with himself:
"You stupid" looking out the window
"No I not" looking at Isaac's seat
"You stupid" looking out the window
"No I not" looking at Isaac's seat
"You stupid" looking out the window
"No I not" looking at Isaac's seat
At this point I turn around in disbelief just in time to see him start beating his head (it looked like the king kong chest beat, but on his head instead of chest). What is so hilarious about this is that it has gotten to where as soon as we get into the caar when we pick Isaac up, the two of them always immediately start argueing, over nothing. It is like it has become part of the routine. I guess this just proves that it is routine to him. And since Isaac was not there to argue with, he decided he would argue with himself!!!!