I've been rewatching a few of these recently, and many of the guest stars (i.e. The Three Stooges, Batman and Robin, Don Knotts, and The Harlem Globetrotters) appear in two or three different episodes. In many cases, most prominently the Harlem Globetrotters, I felt like the second appearance of the guest was better than the first and gave us a chance to know the guest star a little better. That got me thinking, are there any guest stars that appeared once in this series that you think could have benefitted from appearing in a second episode?
I would have liked to see Tim Conway, Don Adams, or maybe Laurel and Hardy appear again. Maybe Sonny and Cher as well.
I was wondering, if Josie & the Pussycats were to appear in another episode, if Hanna-Barbera would have considered doing a cross-over with their 2nd season, set in Outer Space. Could have been fun I guess, but a little too out there for Scooby and the gang at that point in time. I think the Scooby, Shaggy & Scrappy shorts from the 80s could have fit in better with that theme.
I didn't really know that much about Dick Van Dyke when I watched the episode before but learned more over the years and have been watching a lot of The Dick Van Dyke Show lately. So I think another episode with him could have been fun, maybe they could have even managed to get Mary Tyler Moore back then.