Scooby-Doo and Scrappy-Doo (1979 TV series) threatening cancellation for the show, whose ratings were in decline. ABC was going to choose between two shows-Scooby-Doo or an unnamed pilot from Ruby Spears Enterprises. Therefore, for its 1979–1980 season, "Scooby-Doo" was given a major overhaul, adding the character of Scooby's nephew Scrappy-Doo, voiced by Lennie Weinrib, and changing the name of the show to "Scooby-Doo and Scrappy-Doo". Although still present in these episodes, the characters of Fred, Daphne, and Velma became less essential to the plot and Shaggy, Scooby and Scrappy were the main focus. Marla Frumkin took over Pat Stevens' role as Velma Dinkley towards the end
Scooby-Doo the Night" on a flight to one of the development meetings, and decided to rename the dog "Scooby-Doo" and re-rechristen the show "Scooby-Doo, Where Are You!" The revised show was re-presented to CBS executives, who approved it for production. The first episode of "Scooby-Doo, Where Are You!" "What a Night for a Knight" debuted on the CBS network Saturday, September 13, 1969. The original voice cast featured veteran voice actor Don Messick as Scooby-Doo, radio DJ Casey Kasem (later host of radio's syndicated "American Top 40") as Shaggy, actor Frank Welker (later a veteran voice actor in his own right)