The human members of the Scooby Gang are based on four characters from the American TV show The Many Loves of Dobie Gillis, which aired on CBS from 1959 to 1963. Dobie Gillis was transformed into Frederick Herman "Fred" Jones, and Dobie's sidekick Maynard G. Krebs was transformed into Norville "Shaggy" Rogers. Here is a photo of Dobie and Maynard:

Dobie's love-interest Thalia Menninger was transformed into Daphne Ann Blake. Here is a photo of Thalia:

Zelda Gilroy was transformed into Velma Daisy Dinkley. Here is a photo of Zelda talking to Dobie: