Sometime in the late 70s I went to a Saturday matinee. There was always a race to be the first one out after the movie was over (6,7,8-year-olds) and I jumped the gun this time. I thought the movie was over, ran outside and was all alone. Must be the completist in me, but I need to finish watching this movie sometime. Anyway, it was a childrens's movie. It started live-action. A boy had a large box in his room, I think it was a birthday present. Inside was a toy car large enough for him to sit in. When he drove the car out the front of the box, he became animated. If he drove backwards out the other side of the box, he returned to live-action. I think he spent most of the rest of the movie animated. That's all I can remember at the moment. Many thanks to whomever can tell me the title.