At the start of each U.S. TV episode of "The Flintstones", what was the name of the movie showing at the drive-in?

At the start of each U.S. TV episode of "The Flintstones", the name of the movie showing at the drive-in is "The Monster". In the fictional city where the show takes place, Bedrock features a drive-in movie theater where films such as "The Monster" (as seen on the marquee in the original series' opening and closing credits) are shown.

In the opening leader of "The Flintstones", Fred and his family jump into the family sedan. It is powered by Fred's frantically flapping feet. They pick up the Rubble family and arrive at the drive-in movie theater. Dino, the family pet snorkasaurus, is poking his long neck through the car's rag top so the Pebbles and Bamm Bamm (the kids) can get a good view of the movie screen. They all should like the film "The Monster".

With this American animated 1960 - 1966 cartoon show, viewers can often laugh at the impossibly henpecked and middle-class life of Fred and Barney.