 Joe Dante (I) (qv) says that in the original draft of the script,  Gizmo turns into Stripe. But, Executive Producer  Steven Spielberg (I) (qv) overruled this plot element saying that  Gizmo was too cute to be turned evil, and it would be too confusing  for audiences to understand that he is evil for the second half of  the film. This became stressful for Chris Walas (qv) who had  designed the Gizmo puppet only for the actions that happened in the  first half of the movie and had to figure out how to make it work in  the rest of the film, hence why Gizmo is always seen in Billys back  pack for the rest of the film.