Scrappy Days - Page 6:
Scrappy did exactly what he was supposed to do: He got Scooby Doo renewed for another season. I don't think he was a good addition to the format and the fact that he could talk, while his Uncle Scooby sorta couldn't, tore the already-frail "reality," to use that word in the loosest-possible manner. Then again, the underlying premise of "there's no such thing as ghosts" was shredded somewhat during the seasons that the show had guest stars and so Scooby was teaming up with Speed Buggy (a talking car) and Jeannie (a genie). Later, of course, they gave up altogether on the notion that the supernatural did not exist and had Scooby and Shaggy chased by real werewolves and mummies and space aliens.