Dr. Otto and the Riddle of the Gloom Beam is a 1985 American science fiction comedy film starring Jim Varney. It was written and directed by John R. Cherry III. It is the first film to feature the Ernest P. Worrell character. However, it has a slightly darker tone than his later films. The film was released on video in 1992 by GoodTimes Home Video. It was shot in Fall Creek Falls State Park, Boxwell Scout Reservation, and Nashville, Tennessee.

The film is dedicated to famed editor Elmo Williams. A public apology to Williams appears in the end credits, with the promise that if another Dr. Otto film were made, "we'll make it up to you."

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