Bette Davis agreed to do this movie because it was a movie her grandchildren could watch. Also, Davis had three people tending to her on the set throughout the shooting of this movie.
Kim Richards, Ike Eisenmann, and Denver Pyle reprised their roles as Tia, Tony, and Uncle Bené from Escape to Witch Mountain (1975). This movie was also directed by the same director, John Hough, as well as having many of the same technical and production crew.
First of two collaborations of Director John Hough and Bette Davis. They re-teamed for another Disney movie, The Watcher in the Woods (1980).
This movie was unique in its casting of two suspense and horror movie genre legends, Bette Davis and Sir Christopher Lee, as cohort villains. This movie was the only theatrical movie where the pair were teamed together.
Second of five "Witch Mountain" movies. This sequel was released three years after Escape to Witch Mountain (1975). Later came the second sequel, Disneyland: Beyond Witch Mountain (1982), then a television remake of the original, Escape to Witch Mountain (1995), then another remake, Race to Witch Mountain (2009).
Final theatrical movie of Jack Soo (Mr. Yokomoto).
Jack Soo was diagnosed with esophageal cancer in the fall of 1978, just a few months after this movie debuted.
Kim Richards and Ike Eisenmann, who played the children in this sequel, and in Escape to Witch Mountain (1975), appeared in the same scene in Race to Witch Mountain (2009), where Eisenmann was "Sheriff Antony" in the bar, and Richards was "Tina" the waitress. In this movie and its 1975 precursor, their names were similar, being "Tony" and "Tia", respectively.
Director John Hough was instrumental in casting Anthony James as Sickle.
Sir Christopher Lee played an alien in two low-budget science fiction thrillers released the previous year: End of the World (1977) and Starship Invasions (1977).
The name of the youth group was the "Earthquake Gang".
The name of the goat was "Alfred".
The nickname of Mr. Yokomoto (Jack Soo) was "Yo-Yo".
The name of the industrial facility was "Plutonium Industries".
Brad Savage and Kim Richards played brother and sister in No Deposit, No Return (1976).