This movie fails because Zachary Levi doesn't even try to make us believe that he is a specific person in a new body. The movie BIG worked because Tom Hanks captured the specific character of a child in an adult body. In this movie, the adult Billy Batson seems emotionally about five years younger than the child Billy. The child Billy is serious with serious problems. The adult Bill is goofy, giddy, and silly. This child Billy wants to find his mother. The adult Billy wants to eat snack foods. The adult Billy's character disconnects use from any emotional connection with the film. Why should we care about Billy's problems when he himself doesn't? There is some clever stuff in the script that is completely missed by the actor (and apparently the director) that would have helped us make an emotional connection. This is one of the few times where I would say that script was better than the execution of it.