The Darkopolypse Ritual is an ancient and sinister ceremony designed and used by the evil race of Demons that can bring about their 10,000 years age of tyranny upon the Earth called the "Darkopolypse", it serves as a plot element in Scooby-Doo (also known as Scooby-Doo! The Movie).
This ritual deals with using the Demons' mystical relic called the Daemon Ritus and the protoplasmic energy of a thousand good souls including the one most purest soul, which was later revealed to be Scooby-Doo's (as hinted by Velma Dinkley that the final pure soul among nearly 1,000 spirits of innocent human teenagers would not be human).
Scrappy-Doo, now as Scrappy Rex, planned to use the ritual to seek revenge on both his uncle and his former friends, and to destroy Mystery Inc. while leading his newly-building own army of Demons to total domination since he was corrupted by the Daemon Ritus on the Demons' home island which centuries later now became the location of the popular horror resort called Spooky Island.
Daphne fights Zarkos above the island's caves, knocking him through the roof, which exposes the demons to sunlight and kills them using a shine disco ball shaped like a spiked skull. Shaggy confronts Scrappy and rips the Daemon Ritus from his chest, freeing the souls and reverting Scrappy to his original self, before the arrogant Scrappy gets slapped and thrown away with a mere slap by his uncle Scooby. Shaggy finds the real Emile Mondavarious, Spoooky Island's owner, trapped within a hole and frees him. Scrappy and his minions were arrested. Daphne and Fred kiss, Shaggy and Mary Jane hug along with Scooby, while Velma hugs a man she met earlier then punches him while laughing. When Mystery Incorporated addresses the press, Velma thinks that Fred will take credit for her ideas again, however Fred lets Velma take the credit she deserves. Mystery Incorporated is then reunited while Scrappy-Doo and Zarkos are taken away.
- The name "Darkopolypse" is a pun on the 2 words "dark" and "Apocalypse".