 Over the years, plots involved Z-Ro and Jet rescuing a wide range of historical figures, including Genghis Khan, Marco Polo, Magellan, William the Conqueror, Benedict Arnold, William Tell, Christopher Columbus, Blackbeard, Captain Cook, Leonardo da Vinci, Robin Hood, George Washington, Attila the Hun, Hernando Cortez and Daniel Boone.Like early episodes of "Doctor Who", which premiered in the UK more than a decade later, most episodes were melodramatic history lessons for children.No serious effort was made to explain how the time machine worked, and time travel conundra (such as the grandfather paradox) were likewise glossed over.