Miklos Rozsa's score is one of the few movie scores to make extensive use of the cimbalom. The instrument can be seen being played at the beginning of the film.

MGM announced plans to produce the movie with George Pal as producer/director during its 40th anniversary celebration in 1964. Unlike many of the announced projects, this one actually got made but wasn't released until 1968.

This was Byron Haskin's last feature film as director, and the final film that George Pal produced under his contract with MGM. According to Haskin, the studio was so anxious to be rid of Pal that they deliberately sabotaged this film, casting it with the wrong actors, keeping the budget too low and skimping on the all-important special effects.

While Jim Tanner is at the hotel lobby newsstand during a convention on the magazine rack is seen the July 1966 EERIE Comic Book issue #10.

The Woody Woodpecker doll on the news stand outside the convention hall is a nod to Walter Lantz, good friend to George Pal.

The yellow car Jim drives out into the desert is a 1963 Plymouth Sport Fury convertible.

Miklos Rozsa's first film score for nearly five years. Although he lived into the mid-1990s, he did only a handful of film scores subsequently.

When Mrs. Hallson is on the couch in the trailer talking to Jim while he fixes her another drink, by her head is a copy of the September 1966 edition of Mademoiselle magazine.

George Hamilton has a bare-chest scene in this movie.

The footage of Jim driving off the bridge was used nearly twenty years later in Night Train to Terror (1985).