The Flintstones and the Rubbles visit the Bedrock World's Fair, where they visit a time machine exhibit and travel to various times of the future.
Fred, Wilma, Betty, and Barney are visiting a World's Fair when they are persuaded by a dotty scientist to be test subjects for the scientist's time machine. The incredulous four are projected into the future to the times of the Roman Empire, the Knights of the Round Table, Christopher Columbus, Benjamin Franklin, and a post-twentieth century Jet Age. Fred and Barney are placed in the Roman Colosseum and are almost lionosaurus victims for the amusement of a fiddling Nero.
Then, Fred is obliged to fight in a jousting duel in the stead of Sir Lancelot and accidentally prevails in the contest, winning but of course spurning marriage to the King's daughter. Next, the two couples are caught in the middle of a mutiny aboard the Santa Maria and then electrified by Franklin's lightning-struck kite in Philadelphia. Authorities of the Jet Age pursue Flintstones and Rubbles into a Stone Age exhibit at a futuristic World's Fair.
Finally, the four are transported back to prehistory, where Fred berates the scientist's troublesome invention and accuses the scientist of nuttiness, before Flintstones and Rubbles depart their time's World's Fair for home.
- Scientist (only appearance)
- Ducks (only appearance)
- Nero (only appearance)
- Tiberius (only appearance)
- Brutus (only appearance)
- Lionosauruses (only appearance)
- Christopher Columbus (only appearance)
- Columbus' crew (only appearance)
- Sir Galahad (in a chair label)
- Sir Lancelot (in a chair label and disguised by Fred)
- Black Knight (only appearance)
- Arthur (only appearance)
- Guinevere (only appearance)
- Leonore (only appearance)
- Benjamin Franklin (only appearance)
- Hamburger Clerk (only appearance)
- Jet Age Police Officers (only appearance)
- Flintstone home
- Bedrock World's Fair (only appearance)
- Kiddyland (only appearance)
- Hall of Science (only appearance)
- Camelot (only appearance)
- Jousting arena (only appearance)
- Santa Maria (only appearance)
- Philadelphia (only appearance)
- 1964-1965 New York World's Fair (only appearance)
- Time Machine (only appearance)
- Brontosaurus burgers
- Fred's car
|Alan Reed||Fred Flintstone|
|Jean Vander Pyl|| Wilma Flintstone|
|Mel Blanc||Barney Rubble|
|Henry Corden|| Brutus|
|Gerry Johnson|| Betty Rubble|
|Don Messick|| Bamm-Bamm Rubble|
|John Stephenson|| Attendant|
|Doug Young|| Hippo|
- The Flintstones and the Rubles visit the Bedrock World's Fair and the 1964-5 New York World's Fair via a time machine.
- The fiddler playing during the Roman sequence is a parody of Jack Benny as Emperor Nero.
- After the time machine's inventor gets the Flintstones and Rubbles back to the Bedrock World Fair and he asks them what happened, his outfit is a darker shade of blue, then changes back to its lighter shade as before.