Thanks everyone! It's funny because I had not really watched the show, he liked it but I hadn't set down to actually watch it. We went out to eat with a couple and their children and their little boy kept saying "he looks like Mac" I asked what he meant and my son explained who Mac was, needless to say I watched it the next time it was on and I was bowled over on how much he looked and acted like Mac
So for Halloween he went with the Bloo, which I made and he of course was Mac, but everyone that had not seen Fosters didn't think he was dressed up.