"By the pricking of my thumbs, something wicked this way comes" is from "Macbeth" by William Shakespeare, Scene IV, Act I, spoken by the Second Witch. But it may not be technically a Shakespeare quote. More recent experts believe that many of the Witches' scenes, including their songs, were written Shakespeare's pupil Thomas Middleton.
Ray Bradbury first wrote 'Something Wicked This Way Comes' as a screenplay in 1952, after watching Gene Kelly in Singin' in the Rain (1952), which Bradbury thought the greatest musical ever made. Bradbury showed Kelly the screenplay, and Kelly was so impressed that he wanted to make it his next picture. When Kelly shopped the story around to potential backers in 1958, he was unable to raise any money for the project. It was only after this failure that Bradbury rewrote the story as a novel, which incorporated some elements from his 1948 story "Black Ferris," and was published in 1962. Bradbury dedicated the novel to Kelly.
Disney made many changes to the film which writer Ray Bradbury and director Jack Clayton did not intend. Many extra special effects scenes were shot by a second unit director after original production wrapped, and other changes were made before its release. According to the laserdisc commentary by Bradbury, much of his original intentions for the movie were destroyed.
A special-effects sequence that took place at the beginning of the film was cut shortly before the movie hit theaters. In this sequence, the carnival materializes from the smoke of the train, the smoke from the engine "becomes ropes and canvas tents. Tree limbs grow together to form a Ferris wheel and a spider web mutates into a wheel of fortune." This sequence was the first time that computer animation was used to animate organic material, and it was combined with traditional animation. The scene was deemed not convincing enough by Disney executives and was cut from the film at the very last minute. The deleted scene was described in the issue of "Twilight Zone Magazine" released the same month as the film, which assumed the scene was going to be in the final print.