Scrappy debuted on the Scooby Doo program in 1979 as a "new element." Scooby had been on the air for some time by then and the narrow formula of the series had become repetitive to the point where ABC was considering cancellation. One of the very real concerns was whether the writers could come up with the thirteen requisite ghost premises to do another thirteen episodes. Let me tell you how you sold a script to the Scooby Doo series in those days.
You'd go to the producer or the story editor and say something like, "How about a ghost who's an aardvark and he's been haunting ant farms?"
The producer or story editor would consult a list of all the episodes produced to date, and there was about a 95% chance he'd look up from it and say, "Did it in Season Four" or whatever season it had been in. Sometimes, they'd say, "Did it in Seasons Two, Four, Five and I have one in the works right now, same idea." But if you lucked into something in the 5% category, you had an assignment…even if you didn't have a clue who the aardvark would be when he took off his mask or why he was haunting ant farms. Didn't matter. You or someone else could figure that stuff out later. You'd done the hard part.