Before Marty McFly returns Back to the Future, he writes Doc Brown a warning of what will happen to him in 1985, unless he chooses to change history. When Doc discovers the letter, he tears it up, fearing to disrupt the space-time continuum. After Marty returns home, he discovers that Doc had taped the pieces of the letter back together, taking Marty's advice.
These replicas were painstakingly copied from the original props. Die-hard fans will notice that the original 1955 letter and its 1985 counterpart are slightly different from one another. Lou's Cafe stationary matches the film prop exactly. Each of the letters was first written by hand using an old fountain pen, similar to what Marty used. The 1985 version was printed onto aged paper, torn up to match the rips of the original prop, taped back together and further aged to give the edges and tape an authentic yellowed appearance.