Good Humor men are salesman for a specific ice cream company, here parodied as "the bad humor man."
When Mr. Grizzley asks the gang if they need to call their parents, the latter don't claim to be out of their hometown, which may hint that this story took place in their hometown, retroactively named Coolsville in A Pup Named Scooby-Doo (1988).
Unusually when Shaggy and Scooby first hear about the Technicolor Phantoms, they aren't scared. Instead, they react with skepticism, dismissing the concept of "Technicolor Phantoms" as silly.