The sequence "George and Sophia" was originally the first one shot. One year later, the improvisational style of the rest of the film made it feel too scripted, and so it became the last sequence to be re-shot, in order to more closely match the tone of the rest of the film.
When the Doovis family drives onto the Freeway in LA, there were no crew members present in the car. The actors took turns operating the camera as the rest of them improvised their dialog.
Jeffrey Delman: The film's director as the annoyed store manager near the end of the sequence. The grocery store sequences were shot very late at night in an actual supermarket in Los Angeles, and the crew paid for everything that was used/eaten/destroyed during shooting.