Great
I love this so much, it was an effort to get him to smile. For those of you who want to do it without help, this would be a spoiler.
Make an explosion that knocks him on his back (he wont be able to get up). I find it easiest to put on the Bill Gates skin because he says "Nerds can't breathe on their backs!" when it happens. Then simply switch back to the buddy skin and help him up with an open hand. He'll smile. :)