Richard Matheson's book was written as a series of flashbacks so that you got into the cellar with Scott quickly. Universal insisted on a linear story. They also vetoed key sequences, such as Scott spending the night with the female midget, a drunk homosexual who abuses Scott, a gang of teenagers who terrorize him, and Scott becoming a Peeping Tom secretly spying on a teenage baby-sitter. These were rejected as too risqué for 1957.
The special effects technicians were able to create giant drops of water by filling up condoms and dropping them.
Several of the gigantic props (the scissors, nails, and mousetrap for example) were part of the Universal Studio tour for several years.
Richard Matheson had originally written a screenplay for the sequel called "The Fantastic Shrinking Girl" in which Louise Carey begins to shrink herself. Universal had planned to produce it but the project was eventually scrapped.