Velma's famous line, "My glasses, I can't see without them!" was not originally scripted for the show. During a table read for the voice artists, Velma's voice-over actress Nicole Jaffe, who was near-sighted as well, lost her glasses and uttered a variation of what became Velma's famous catchphrase. The writers liked the line so much that Velma losing her glasses became one of the show's trademark gags. Velma loses her glasses in the first episode, What a Night for a Knight (1969), but the actual line is first spoken in Decoy for a Dognapper (1969).
Frank Welker wanted to audition for the role of Shaggy since he had always been cast as the straight man and wanted to do a comedic character. Casey Kasem wanted to audition for the role of Fred because he claimed he was not a comedic actor.
Under the title of "W-Who's S-S-Scared?", this series was originally rejected by CBS executives, who thought the presentation artwork was too frightening for children and that the show must be the same. CBS Executive Fred Silverman was listening to Frank Sinatra's "Strangers In The Night" (with the scatted lyric "dooby-dooby-doo") on the flight to that ill-fated meeting. After the show was originally rejected, a number of changes were made: the Hanna-Barbera staff decided that the dog should be the star of the series (instead of the four kids) and renamed him Scooby-Doo (after that Sinatra lyric), the spooky aspects of the show were toned down slightly, and the comedy aspects tuned up. The show was re-presented, accepted, and presented as the centerpiece for CBS's 1969-1970 Saturday Morning season.
"Too Much" (later Scooby-Doo) was originally written as a Great Dane, but fearing their creation would be too close to the titular character in the comic strip "Marmaduke," creators Joe Ruby and Ken Spears changed Scooby/"Too-Much" to be a big, sloppy sheepdog (which itself was far too close to "Hot Dog" from the "Archie" comics that inspired the series). After meeting with Hanna and Barbera about the issue, Scooby was changed back to a Great Dane. Character designer Iwao Takamoto went to a dog-breeding colleague at the studio for advice on what elements made up a prize-winning Great Dane, and then preceded to break every "rule" in his design of Scooby, including the double-chin, the bow-legged hind-legs, and the spots on his back (No *real* Great Dane has spots). Scooby's utter lack of prize-winning characteristics is spoofed in Decoy for a Dognapper (1969).
Shaggy's real name is Norville Rogers.