Several people call Elaine Zacharides (played by Margaret Hamilton) a witch. Margaret is even carrying a broom when we first see here, which Charles points out. Margaret Hamilton played the Wicked Witch in The Wizard of Oz.
William Castle was able to get popular child actor Charles Herbert to play Buck by offering to give him top billing. Charles Herbert would appear in this and two other features in this year before roles in features completely dried up. He would complete his career in television roles.
The exterior of the Cyrus Zorba House that the family inherits is in reality the Winchester Mystery House located in San Jose California. This is not the main entrance "street view", but is from one of the other many entrances of the house. Notice the handrail running up the middle of the steps so that it's easier (and safer) for public use.
William Castle: [gimmick] The movie was filmed in "Illusion-O" and a special viewer was needed to see the ghosts. This resulted in a number of sources incorrectly stating that the film was originally shown in 3D. The "ghost viewers" contained a red filter and a blue filter, but unlike 3D viewers/glasses, both eyes would look through the same color filter. The red filter would cause the ghostly images to intensify while the blue filter caused the images to fade.