Jerry Maren, who plays the pitcher in the kitchen baseball scene, was actually an actor in the original The Wizard of Oz (1939) movie, where he uncredited played a Lollipop Guild Member Munchkin. Maren later said he regretted making Under the Rainbow (1981) because it was in such poor taste and nothing remotely like what ever happened while filming The Wizard of Oz (1939).
The film was nominated for two Razzies - Worst Musical Score and Worst Supporting Actor (Billy Barty) at the 2nd Golden Raspberry Awards in 1982, but the movie failed to take home a gong in either category.
The high majority of the cast in non-leading roles played characters who were billed each as a Hotel Rainbow Guest. There were no less than 106 actors and actresses in the movie who were billed as Hotel Rainbow Guests.
Some movie posters for the film featured a long blurb that read: "Somewhere, Under The Rainbow, way down low - Chevy Chase, Carrie Fisher and 150 midgets are fighting valiantly to save our country against all Oz!".
The film's "Under the Rainbow" title is derived from the famous song sung by Judy Garland from The Wizard of Oz (1939) of which this movie is a partial comical fictional making-of film about. The tune is often known as "Somewhere Over the Rainbow" and had its music composed by Harold Arlen with lyrics written by E.Y. Harburg.
According to the 'Mutant Reviewers' website, "part of the inspiration for Under the Rainbow (1981) comes from rumors that the little people did party hard and tear apart the hotel they stayed at during filming of The Wizard of Oz (1939). Those rumors do not seem to be true, but were used as basis of this film".