A life-long fan of camping, Jeff Daniels has owned an RV for years. According to a Detroit radio interview, his RV driving lessons for the movie were quickly canceled when he arrived on location in his personal recreational vehicle.
The Munro RV is a Forest River, Georgetown 359 TS. Five of them were purchased, plus a sixth which was ordered in pieces and assembled in a way that allowed hydraulic rams to raise and lower it out of the lake. Two were fitted with special suspension hydraulics to handle some of the extreme driving moments. Two of them are the ones that the Munros are seen living and driving in. The 5th was dubbed "Wild Thing" and was fully functional.
The script originally called for a 1990s recreational vehicle, but Sonnenfeld wanted something more classic. His search yielded two 1948 "Flexible Clippers," which were used in the '40s and '50s by such companies as Greyhound and Trailways. Both were in reasonably good shape when the production acquired them. The seats were stripped away, the bodies restored and painted an eye-catching red and cream (they were originally blue and white) and outfitted like vintage motor homes. Other exterior appointments included "eyelid" shades over the headlights, a chrome ladder up the back and a wooden roof rack to complete its distinctive classic look. The second bus was completely rebuilt, including engine and drive train, with only about 60 percent of the interior restored. It was used mainly for stunt work and second unit exterior shots.
The scene where Jamie, Cassie and Carl are listening to music on the headphones and singing to different songs all at once, driving Bob mad, was actually based on a real life incident to happened to Barry Sonnenfeld. Barry and a film crew were filming a documentary in Japan and during a bus ride, Barry and the crew wore headphones, each of them listening to different song and singing the different songs out loud.
Throughout the film, a man's humming is used in the score. According to Barry Sonnenfeld, it is actually supposed to be the voice of God. The humming would appear when something disastrous in the movie would happen.