Happy Halloween, Scooby-Doo! is the thirty-first in a series of direct-to-video films based upon Hanna-Barbera's Scooby-Doo Saturday morning cartoons. It was released on September 15, 2020, as a Walmart movie exclusive, before a general release everywhere on digital HD and DVD on October 6.
It's marketed as the first Halloween-themed movie, despite the fact, there has already been Scooby-Doo! and the Goblin King and Scooby-Doo! and KISS: Rock and Roll Mystery, as well as the DTV short film Scooby-Doo! and the Spooky Scarecrow.
After defeating the Scarecrow, Mystery Inc. think they've saved Halloween for everyone in Crystal Cove, but the nightmare is not over as the Jackal-Lanterns come to life and attack everyone. With help from Elvira, Mistress of the Dark, and Bill Nye, the gang must overcome this menace before they over run the town!
On Halloween night, at Elvira’s Halloween of Horrors Parade in Crystal Cove, Mystery Incorporated is trying to capture the Haunted Scarecrow.
The Haunted Scarecrow comes flying out of a store window and begins to terrorize the parade crowd with gas grenade drones, while Shaggy and Scooby hide out in the Mystery Machine, eating candy and enjoying each other’s company.
A party float crashes into the Mystery Machine, throwing it into the air! The Mystery Machine crashes on the ground, smashed.
Velma hacks into the drones, disabling them, and pins the Haunted Scarecrow to a tree.
He is unmasked and revealed to be “regular” Scarecrow, or rather his alter ego, Dr. Johnathan Crane, a recent escapee from Arkham Asylum.
Daphne tries to get Dr. Crane to say the infamous “Meddling Kids” line but he doesn’t, because he claims he is “getting away with it.”
Suddenly, a bunch of yellow drones carrying canisters of fear gas come flying out of nearby buildings.
Everyone begins to panic, but soon the drones begin exploding, with Shaggy and Scooby shooting them with pieces of Halloween candy.
The Mystery Inc. gang is treated as heroes by the parade-goers and everyone begins to party, but the Sheriff shuts them down, as the area is now a federal crime scene.
Velma reveals that they were able to catch him because they traced a piece of fan mail sent to Elvira back to him. She then explains that they tracked a gas leak with an air quality meter that she assumed was from him.
Right before Dr. Crane is taken away by the feds, he claims that he only steals Toe Omnitech gear, and that it doesn’t leak, implying that the tracked gas leak was from something else. He says to Velma that, while he is caught in chains, they are both stuck “in the same trap.”
Fred goes to the Mystery Machine, which looks wrecked beyond repair.
Shaggy and Scooby decide to trick ‘r treat while they can because they aren’t scared of solving a mystery at the moment. They throw together costumes made out of Halloween candy and head out to begin the festivities.
They head towards a pumpkin patch, where one of Dr. Crane’s drones is lying, glitching and breaking down. Shaggy rubs off some dirt and sees the words “Tot AlLi Frame” engraved into the drone.
They notice a truck full of toxic waste leaking into the pumpkin patch.
Suddenly, one of the pumpkins touching the toxic waste grows a face and comes to life! Many pumpkins begin to come to life, including a ginormous one, which begins stalking towards Shaggy and Scooby.
The smaller pumpkins begin to fly, chasing Shaggy and Scooby. Scooby accidentally swings a branch at one of the pumpkins, smashing it and chasing off the others.
Meanwhile, the rest of Mystery Incorporated has a run-in with the Sheriff, who tells them that ever since they captured the Trash Monster of Scranton, he’s been telling them not to mess with law enforcement. He warns them that they brought “whatever happens next,” onto themselves, thus there's blood in their hands as well. The gang is confused, as they caught Dr. Crane, but they ignore his warning, as they know they did the right thing in catching him.
They meet Mike and Michelle, a father and daughter pair of civilians who are thankful that they caught Dr. Crane. Mike offers his help to them, if they ever need it in the future.
They then begin to be interviewed by a group of television reporters but Shaggy and Scooby run in, trying to tell everyone about the living pumpkins, whom they name “Jackal-Lanterns.”
Daphne takes Shaggy and Scooby away to try and calm them down, as people don’t believe them about the Jackal-Lanterns.
Bill Nye calls Velma and Fred, who are just finishing up their interviews, and tells them that he gets them a gift. A package flies in from the sky and transforms into the “Mystery Machine X,” a white, modern, electric version of the Mystery Machine. When they go inside, Bill Nye pops up as a hologram, who tells them that he will be able to guide them when they are in the car. While Velma loves the new car, Fred is less excited, as he wants to keep the old Mystery Machine.
The reporters suddenly scream, and when Velma and Fred get to them, they say that one of the reporters was taken by flying pumpkins!
Meanwhile, Elvira is packing up her car and Daphne runs up to her, asking if she would be willing to mentor her. Elvira agrees and starts by having Daphne load her luggage into the car.
Back where Shaggy and Scooby are, another pumpkin comes to life and grabs onto Shaggy!
Fred and Velma find the reporter in the pumpkin patch, but they are too late, as she is eaten by the giant Jackal-Lantern and is spit out, now transformed into a Jackal-Lantern herself.
The gang all begins to run away from the Jackal-Lanterns where they are. They all meet up in the center of the town, but they are separated by a giant crack in the ground, which has begun to form. Shaggy and Scooby run into the car of Mike and Michelle, who are running away themselves.
Now, with the gang separated in three different cars, Fred and Velma in the Mystery Machine X, Daphne with Elvira in her car, and Shaggy and Scooby with Mike and Michelle, they all drive onto the highway to escape the Jackal-Lanterns who are following them closely behind.
A long car chase ensues!
The gang eventually catch up with the Sheriff on the highway, who still doesn’t know about the Jackal-Lanterns. Velma asks to be patched through to the Feds’ truck, where Dr. Crane is being held. When the Sheriff notices that the Jackal-Lanterns are driving cars and following them, he freaks out and falls behind, soon getting consumed by Jackal-Lantern crowd.
Velma finally gets into the Feds’ truck, where Dr. Crane is held and, accompanied by Shaggy and Scooby, goes to question him.
Dr. Crane claims he has nothing to do with the Jackal-Lanterns and offers to help the gang beat them. Velma agrees, trusting him, and gives him his Scarecrow gear.
Everyone crosses into Elvira’s car and while Scarecrow holds off the Jackal-Lanterns, allowing everyone to get ahead of them, he is soon grabbed and consumed by them.
Elvira’s car runs out of gas, just as the Jackal-Lanterns start to catch up with them. Everyone gets out of the car and runs into the nearby woods.
Fred, with his shirt ripped off and battle-paint on, begins to set a giant-scale trap for the Jackal-Lanterns.
Velma tries to concentrate to go to her “mind palace,” but can’t get there. Shaggy suggests that if they all take Scooby snacks, Shaggy and Scooby and Shaggy will be able to join them there. They all take Scooby snacks, and they are suddenly transported into her mind-palace, which is a fantastical visualization of the Mystery Machine floating in space.
They begin to revisit events that took place earlier on that night, and Velma begins to piece the mystery together.
They arrive back in reality, where the Jackal-Lanterns are almost at Fred’s trap.
They begin to fight off the Jackal-Lanterns, smashing them left and right! When it appears as if they’re outnumbered, Velma takes a leap of faith and, trusting that the Jackal-Lanterns aren’t real, jumps into the mouth of the giant one.
It suddenly shuts down, and Velma comes out safely, revealing that the giant Jackal-Lantern was mechanical and all the smaller ones were drones. She reveals that what was actually written on the drones was T.O.T. Aluminum Lithium Frame.
All the people who were consumed by pumpkins are found trapped inside of the giant Jackal-Lantern, except for the Sheriff and Dr. Crane.
Velma begins to explain that there was a proposed lithium mine in Crystal Cove but that it was never approved, because it would damage the environment, like the collapsing of the town square.
A hologram begins to play from the giant Jackal-Lantern, with the Sheriff revealing that he was behind the whole scheme. He is actually a man named Culter Toe, the head of Toe Omnitech, who was also behind the mystery of the Trash Monster of Scranton. After being released from jail, he began to disguise himself as a local Sheriff to drive the gang out of business, hence he planned the whole scheme so that he could mine the lithium without interference from Mystery Inc.
Velma tracks his hologram's location and the Feds start heading towards where he is. Just before his hologram cuts off, the Scarecrow jumps onto his car, ultimately capturing him, allowing the Feds to confiscate his car.
Now that everything is ok, and Toe is back behind bars, the gang heads to a Halloween party to enjoy the rest of Halloween! Elvira is talked into giving her wig to Daphne to complete her outfit after having already switched clothes, but Elvira hasn't been wearing a wig, but a macaque, who needs to be fed fruit a couple of hours. She then walks off onto a stage with curtains, saying goodbye to an unseen audience, then she makes an even bigger surprise than before by turning her head around to reveal a spider-like face, and wishes the audience a "Happy Halloween!"
The gang gets help from Nye in building the Super Mystery Machine, although Fred changes the blueprints to simply rebuild the old Mystery Machine; Shaggy and Scooby look for parts in a junkyard and imagine what they find to be food, perhaps versions of their own mind palaces. The gang pay off Nye by working at a kitchen.
- Bill Nye
- Haunted Scarecrow
- Dr. Jonathan Crane
- Alpha Jackal-Lantern
- Agent Malarkey
- Victoria Haselbum
- Red Herring (Cameo)
- Farmer Morgan
- Mrs. Malvo
- Phyllis Diller
- Three Stooges
- Uncle Ernie
- Daily Stuff
- Scooby Snacks
- The Crystal Epitaph
- The Mystery Machine
- Mystery Machine X
|Cutler Toe as the Sheriff and the Alpha Jackal-Lantern||He disguised himself as the Sheriff to drive the gang out of business so that he could mine for lithium without their interference.|
|"The Spookiest Time of the Year"||Written by Maxwell Atoms &
|Morgan Kibby &|
|"Look At Us Now"||Written by Andy Sturmer||Susanna Benn &|
|Matthew Lillard||Shaggy Rogers|
|Grey Griffin||Daphne Blake|
|Kate Micucci||Velma Dinkley|
|Dwight Schultz||Scarecrow/Jonathan Crane|
|David Herman||Sheriff/Cutler Toe|
|Roger Craig Smith||Autopilot|
|Fred Tatasciore||Alpha Jackal-Lantern|
- The Sheriff from the two previous DTV movies comes back and is revealed to have been the villain all along, having him be a culprit of an old case of the gang (which happened off-screen). This came with literal flashbacks to those two movies during the reveal, giving a conclusion to this "trilogy".
- The members of the gang are called "young adults", which means they are 18 or over. This means that the events of this film take place at least a year after Scooby-Doo! and the Curse of the 13th Ghost.
- Velma's attitude in the previous two films is also explained, thus giving a conclusion to her arc.
- When Velma was interviewed, she said "We've been doing this forever, since we got a pup named Scooby-Doo", which refers to them starting solving mysteries from a very young age as the Scooby-Doo Detective Agency.
- Scarecrow first appeared in the Scooby-Doo! Team-Up stories Who's Scared? and A Super Friend in Need. He later made a cameo appearance in the DTV Scooby-Doo! & Batman: The Brave and the Bold. Despite not being references to those encounters, the movie doesn't contradict them either since Mystery Inc. seemed to have already been familiar with him. Crane didn't seem to know the gang's members' names until later in the movie but he didn't have much of an interaction with them in his previous appearances.
- Elvira first appeared in one of the previous DTV Scooby-Doo! Return to Zombie Island.
- Bill Nye first appeared in the Scooby-Doo and Guess Who? episode Space Station Scooby, making this the first modern show that has a direct connection with a DTV.
- The setting of Crystal Cove is used in the movie, which was the place the Gang lived during Scooby-Doo! Mystery Incorporated.
- Daphne calls Fred, "Frederick Herman Jones". The middle name was first addressed in the DTV Aloha, Scooby-Doo!
- Shaggy mentioned "having solved three cases with Phyllis Diller until they found out". They found out that either it was Daphne in disguise or that Daphne was slowly trying to take over her life. While it most likely refers to the former due to the personality adopted by Daphne in this film, it could be taken as the latter and have it be a direct reference to the The New Scooby-Doo Movies episode A Good Medium is Rare, in which they do solve a case with Phyllis Diller.
- Elvira asks Daphne if she has done circus work before, to which she replies "Not officially for a circus, no." This either means that she did it for fun or that she did do it for a circus, but not officially. While it most likely refers to the former due to the personality adopted by Daphne in this film, it could be taken as the latter and have it be a reference to the few times in which she did do some circus stunts, some of those include the Scooby-Doo, Where Are You! episode Bedlam in the Big Top, and the DTV Big Top Scooby-Doo!
- Red Herring, a recurring character from A Pup Named Scooby-Doo, makes a small cameo and his truck is seen during the chase scene.
- Fred mentions having solved the case of "The Ghosts of the Three Stooges". They did meet the actual Three Stooges in the The New Scooby-Doo Movies episodes, Ghastly Ghost Town and The Ghost of the Red Baron.
- Fred screaming over the destroyed Mystery Machine is a reference to the final scene of the movie Planet of the Apes.
- Happy Halloween, Scooby-Doo! | Cast Interview & Sneak peek with director Maxwell Atoms and the voice cast (Frank Welker, Grey Griffin, Matthew Lillard, Kate Micucci and Cassandra Peterson) was posted online on October 11, 2020.
- How Mystery Inc. got The Mystery Machine back after Fred sold it in Scooby-Doo! and the Curse of the 13th Ghost is unexplained. However, it is likely this film takes place before those events.
- The final credits scene parodies the 1931 movie Frankenstein with Fred declaring "It's Alive!".
Animation mistakes and/or technical glitches
- None known.
Inconsistencies/continuity errors and/or goofs/oddities
- At one point, the Mystery Machine X is seen being driven by the Jackal-Lanterns.
- During the battle with the Jackal-Lanterns, Elvria's loses one of her black high-heeled shoes, the left one. Daphne subsequently retrives it, however it now appears to be a right shoe.
- When Shaggy tells Daphne "You gotta make candy to earn candy" she uses a pencil with her phone.
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