Slang's space cadet `an eccentric, especially one who is stuporous or out of touch with reality' evolved from  Tom Corbett, Space Cadet,  a 1950 television series depicting the adventures of a 24th-century cadet in the Solar Guides, the interplanetary police force keeping order in the Solar Alliance.
Space Cadet aired in the year 2000, and it depicted the adventures of a 21st century policeman.