Just finished rewatching the whole two-season DVD box set

Contains 23 out of the 24 episodes (absent is S1's Wednesday is Missing, featuring the Addams Family, due to licencing issues). For this series (which followed Scooby-Doo, Where Are You!), each episode featured a guest star or stars (some real-life, some Hanna-Barbera fictional characters). I hadn't seen most of these since first broadcast.

Season one;
Ghastly Ghost Town (The Three Stooges) ~ 5/10
The Dynamic Scooby-Doo Affair (Batman and Robin)~ 6/10
The Frickert Fracas (Jonathan Winters) ~ 5/10
Guess Who's Knott Coming to Dinner? (Don Knotts) ~ 7/10
A Good Medium Is Rare (Phyllis Diller)~ 7/10
Sandy Duncan's Jekyll and Hyde (Sandy Duncan) ~ 6/10
The Secret of Shark Island (Sonny and Cher) ~ 8/10
The Spooky Fog of Juneberry (Don Knotts) ~ 7/10
The Ghost of Bigfoot (Laurel and Hardy) ~ 7/10
The Ghost of the Red Baron (The Three Stooges) ~ 5/10
The Ghostly Creep from the Deep (The Harlem Globetrotters) ~ 7/10
The Haunted Horseman of Hagglethorn Hall (Davy Jones) ~ 7/10
The Phantom of the Country Music Hall (Jerry Reed) ~ 5/10
The Caped Crusader Caper (Batman and Robin) ~ 4/10
The Loch Ness Mess (The Harlem Globetrotters) ~ 8/10

Edit (7 February 2022): Found the 'missing episode' Wednesday is Missing online ~ 8/10


Season two;
The Mystery of Haunted Island (The Harlem Globetrotters) ~ 7/10
The Haunted Showboat (Josie and the Pussycats) ~ 8/10
Mystery in Persia (Jeannie) ~ 6/10
The Spirited Spooked Sports Show (Tim Conway) ~ 5/10
The Exterminator (Don Adams) ~ 7/10
The Weird Winds on Winona (Speed Buggy) ~ 7/10
The Haunted Candy Factory ('Mama' Cass Elliot) ~ 7/10
The Haunted Carnival (Dick Van Dyke) ~ 6/10

A few very good episodes, several okay episodes - and far too many poor ones. When this series is bad, it's BAD. Instead of making the most of its longer-than-usual 43 minute format, many of the episodes feel they're just over-extended reworkings of standard 22 minute scripts. The result is they feel drawn-out, repetitive (especially in the chase scenes), and at times boring.

Nevertheless, Frank Welker (Fred), Casey Kasem (Shaggy), Heather North (Daphne), Nicole Jaffe (Velma), and Don Messick (Scooby) all bring their A-game. And despite the stretched-out feel, there is some very funny writing, and some great atmospheric settings.

Overall, 6.5/10