In Scooby-Doo on Zombie Island (1998), Mystery Inc. were presented as adults with jobs. Daphne and Fred were television journalists on a show where she was also the hostess, Velma owned a bookstore, and Shaggy and Scooby were US Customs agents. However, the floating timeline of the direct-to-video series has retconned them from adults back to teenagers. This movie is established as taking place less than a year after Scooby-Doo! and the Curse of the 13th Ghost (2019), where they were stated to be on the verge of turning 18. This resulted in some impromptu, and often unconvincing, retcons to explain some of the scenes shown in flashback. For example, Daphne's journalism is changed to her being on a school project, which for some reason gained interest from Chris the talk show host. The bookstore and Customs bits are simply never mentioned.
One of several Scooby-Doo productions released in 2019, the 50th anniversary of the Scoobyverse which was "born" in 1969.
Of all the main guest characters from Scooby-Doo on Zombie Island (1998), Beau Neville is the only one who does not appear in flashback nor have a present-day lookalike in this film.
Cassandra Peterson's iconic character Elvira appears in the Scoobyverse for the first time, after having been caricatured in numerous television productions in the 1980s. And also as Drella Diabolique, also voiced by Peterson, in Lego Scooby-Doo!: Haunted Hollywood (2016).
Second Scooby-Doo film to be a direct sequel after Scooby-Doo! and WWE: Curse of the Speed Demon (2016).