I think kids are so happy for a couple of reasons, they don't have a care in the world about bills or responsibilities. They are allowed to imagine things and dream big. The last thing is they find great joy in little things.
Remember Michael Winslow, the guy that could do all the sound effects in the movie Police Academy? He is the real thing, I have seen many performances of his talent to be able to copy sounds, leading me to believe that he really did all those sounds in the movie.