One of the things that I really didn't like when they finally got around to catching the 13th ghost in Scooby-Doo! Curse of the 13th Ghost, was how they just nonchalantly swept the existence of Scrappy under the rug with the grownup Flim Flam asking "Where's Scrappy?" and the response was "What's a Scrappy?"
Yeah, I know people hate Scrappy, but the thing is that Scrappy was badly mishandled after his introduction and practically saving the Scooby franchise from fading into obscurity. He at least deserved a departure from the franchise with dignity. Remember the episode from the 13 Ghosts of Scooby Doo, It's a Wonderful Scoob, where Scooby quits the gang? Vincent Van Ghoul showed Scooby a dark future where Scrappy no longer worshipped his uncle and called Scooby a worthless coward. The reason why they never caught the 13th Ghost had Scooby quitting his responsibility for a SECOND TIME due to a nervous breakdown. This could have been a good reason for Scrappy to become disillusioned with his uncle, lose all respect for him and leaving him. Who knows? Maybe we can have Scrappy forced to live on his own and eventually grow up, lose that childlike and impetuous behavior and become the hero that his uncle never was. There was some potential that lacked a good writer at the time.
The Curse of the 13th Ghost wasn't a retcon. It was a cheap and extremely clumsy movie that really didn't make sense in terms of continuity, especially with Velma's so-called explanation of mass hallucinations due to high altitudes. It was a money grab and was riding on the cult following of the original 13 Ghosts series. I liked the idea that the Scooby gang screwed up a mystery. They were untrained, amateur teen detectives and it had to happen sooner or later. Zombie Island showed the gang going their separate ways in the beginning and had them finally discovering that magic and ghosts are REAL and it allowed them to grow up. I wish they could have used this opportunity to let Scrappy grow up. They let Flim Flam grow up.