In the scene where Roy Fuchs (Jack Warden) walks up to Rudy (Kurt Russell) and Jeff (Gerrit Graham) as they're finishing shoveling dirt over the spot where they buried Luke, Graham didn't have any lines and kept pestering Robert Zemeckis and Bob Gale for lines. Finally, he just decides to repeat whatever Russell said to Warden. Apparently Warden was unaware of what Graham was doing, thus his line "What're you? A fuckin' parrot?". It was Warden's genuine annoyance at Graham, which worked so well in the scene that it was included in the final cut.
The stunt coordinator felt the impact of the 1974 Mercury Montego jumping the train, and hitting the pavement was too much for a stunt driver to take. So, a dummy was put in the driver's seat, and the car was pushed toward a ramp at high speed, and let go.
Robert Zemeckis and Bob Gale have said that there were attempts to sabotage the filming, claiming that there were props stolen from the set, and that reports were made to executives at Columbia Pictures saying that Zemeckis and Co. were out of control.
Roy L.'s line about "politicians staying bought" was first attributed to steel baron Henry Frick about President Theodore Roosevelt after massive donations to the Republican party by big business helped Roosevelt's reelection and Roosevelt subsequently began proposing legislation to increase regulation of steel mills and railroads.
According to Robert Zemeckis and Bob Gale, the film's release was botched by the studio. The film tested extremely well in previews and Columbia Pictures pushed the film out of its original late-August release date to mid-summer with little publicity and poor advertising. The film only played across half the United States rather than receiving a true wide-theatrical release and consequently flopped upon release.
After the commercial where Jeff shoots up the cars on Roy Fuchs's lot, he is interviewed by the FBI. In the scene, he blames the attack on Arab terrorists. At the time of this movie's release, the Iran hostage situation was going on. According to Bob Gale in the DVD Commentary, an alternate version of the scene was shot in which Jeff blames a different group for the act in case the Iran situation was resolved before the film was released. It wasn't and Jeff's false accusation was still relevant when the film came out.
According to Bob Gale in the Commentary, producer Steven Spielberg was appalled by Rudy's line about President Jimmy Carter: "Hey, he fucks with us..." Spielberg was a supporter of Carter. Robert Zemeckis and Gale refused to remove the line because where they came from (Gale is from Missouri and Zemeckis is from Chicago) politicians are (in their opinion) corrupt.
Zemeckis was walking across the set when he spotted two bikers hanging out with two nuns. He immediately summoned the camera crew and they shot a scene with the bikers walking up and taking hot dogs away from the nuns and the nuns retaliated by grabbing their beers and slamming them down. Normally, production assistants pour out the beer and replace it with water, but, the nuns slammed down actual Coors beer and promptly spit it out. Columbia execs nixed the scene because one of them was a devout Catholic.
Robert Zemeckis and Bob Gale had originally developed the script for Universal, but when that studio passed on it they took it to Columbia Pictures, which was the co-production company of 1941 (1979), which Zmeckis and Gale had written. Columbia head Frank Price loved the script and quickly greenlit the film. Steven Spielberg, who was directing "1941" at the time, would go on to executive-produce this film.
The scene where Rudy's commercial in the parking lot of the football game was re-shot because Columbia Pictures executives were appalled by the "Dicknose" glasses that Gerrit Graham wore in the scene. Snippets of it could be scene in the final cut of the film when Kurt Russell holds the glasses at the camera for an instant as his scenes were not re-shot.
At the football game when Michael McKean and David L. Lander hack the satellite, just before the camera comes on you can see the two original "penis noses" in a box. These were the original gags for Gerritt Graham and Kurt Russell, but Columbia executives put the kibosh on those gags, replacing them with bouncing eyeball glasses.
According to Kurt Russell on the DVD Commentary, he kept having trouble saying the line "Best salad bar in town: Airport Lanes!". After constantly flubbing the line, Robert Zemeckis had to mouth the line to Russell so he would get it right.
The trivia item below may give away important plot points.
Jack Warden initially rejected the role of Roy Fuchs. Later, Robert Zemeckis and Bob Gale were told by an acquaintance that actors like roles in which they can either act drunk, play dead or perform multiple roles in the same film. Gale and Zemeckis then offered the additional role of Luke to Warden, which gave him the chance to play 2 roles AND play dead, and he accepted.