In Star Wars: The Clone Wars, one character whose Jedi name is Sha'a Gi is based off of Shaggy from Scooby-Doo, in both name and appearance.
The video above can be watched for more information. Thanks so much to Thomas for sharing this with me!
Asmodeus from Scooby-Doo! Curse of the 13th Ghost is in fact not an originally created name. In religious mythology, Asmodeus is name of the King of Demons (fitting I suppose, for the final ghost in the chest).
It is incredibly likely that the reason which "Wednesday is Missing" cannot be released on the (Almost) Complete Collection of The New Scooby-Doo Movies is John Astin.
Though Hanna-Barbera was able to release their 1970s cartoon version of The Addams Family on DVD, this version did not include John Astin and Carolyn Jones as the voices of Gomez and Morticia, respectively. "Wednesday is Missing" was the final time Jones would ever provide Morticia's voice. However, John Astin returned to voice Gomez in a 1990s cartoon adaption of The Addams Family, which HB has also been unable to release.
In "The Weird Winds of Winona" from The New Scooby-Doo Movies, two notable discontinuities with the Speed Buggy series are present. Firstly, Speed Buggy's remote is typically red, however, in this episode, it is shown as black throughout the entire episode. Mark's skin complexion is also oddly shown as being significantly lighter than it is in the Speed Buggy series, which was animated and aired at the same time that this episode was.
According to an interview on A Podcast Named Scooby-Doo, Grey Griffin (Daphne's voice actress) sounds very similar to Daphne in real-life.
Zomba, one of the 13 ghosts from the demon chest in "That's Monstertainment" (The 13 Ghosts of Scooby-Doo) was the only female character in the show not to be voiced by a female. She was voiced by Les Tremayne, who was most famous for being part of the main cast of the Shazam live-action series in 1974-1977. A picture of him is below (thought it would be interesting to include it, as quite honestly he does not look like he's the voice of that character!)
In 1998, Cartoon Network released the Scooby-Doo! Ghoul Gallery coloring book, which includes an absurd zombified redesigning of a random side-character, C.L. Magnus's butler, from "Go Away Ghost Ship" (Scooby-Doo, Where Are You?).
Photo credit: ScoobyAddict
The horror musical comedy film Hillbillys in a Haunted House bears some striking similarities to Scooby-Doo, and more specifically, Scooby-Doo Meets the Boo Brothers. The concept of "splitting up" is present, one character is named "Jeepers," Jeepers jumps into another character, Woody's arms whenever he is scared, and the general tone and plot of the movie is very similar to that of a Scooby-Doo episode.
There are also significant similarities to Scooby-Doo Meets the Boo Brothers in this film. This film features an old Civil War plantation as its setting, features multiple ghosts running around the house, three of which are an ape, a skeleton, and a Civil War general's ghost. The Civil War general ghost is implied to be a real ghost at the end of the film. Even more eerily, the name of the mansion is quite literally the Beauregard Mansion!
This film came out in 1967, before Boo Brothers or the Scooby-Doo franchise, so it is possible that some minor elements of this film may have inspired certain ideas for Boo Brothers or the Scooby-Doo franchise.
On the DVD covers for both Scooby-Doo Meets the Harlem Globetrotters and Scooby-Doo and the Monster of Mexico, Daphne's scarf is inexplicably purple instead of its normal green.
Thanks so much to The Cop for coming up with this fun fact!
Despite that contract issues with Charles Addams prevent "Wednesday is Missing" (aka "Scooby-Doo Meets the Addams Family") from being released in the US, the episode was released on VHS in Australia by Worldvision Home Video.
Credit for finding this fun fact goes to Deandre.