Mystery Inc. travels to Loch Ness in Scotland to see the famous Blake Castle, where Daphne's cousin Shannon lives, and where the Highland Games are being held. But there's a problem. Apparently, there was a recent attack by none other than Nessie herself. Shannon also claims to have seen the creature before, and claims that it is real, siding with local enthusiast Del Chillman and Professor Pembrooke, a scientist who staked her whole career on proving the monster's existence. However, Sir Ian Locksley, the head judge of the games, thinks just the opposite, causing a mutual hatred between him and Pembrooke.
The next night, Shaggy and Scooby are chased by the monster, ruining the game field in the process. The gang searches the area for clues, and sure enough, they discover that the monster tracks lead into town instead of toward the loch. Whether they like it or not, they've got a mystery on their hands.
Grey DeLisle returns voicing Daphne and remains as such from here through the rest of the franchise so far. It’s also the first time Mindy Cohn voices Velma in the films after first assuming the role in What's New, Scooby-Doo?. She would remain in the role until 2015.
Also, as from here until Scooby-Doo! and the Samurai Sword, this movie has Mystery Inc. wear their outfits from What's New, Scooby-Doo?, and has them voiced by their regular voice actors, no longer having the retro feel of the previous two films.
This film contains examples of the following tropes:
- 2D Visuals, 3D Effects: The Loch Ness Monster itself is clearly made using CGI.
- Ambiguous Gender: Nessie is referred to by female pronouns, despite having no indication of their gender. Lampshaded by Fred.
- Artistic License – Geography: There is no “Blake Castle” on the shores of Loch Ness, there is a Blake’s Castle
but it is in Ireland not Scotland, it’s likely based on the famous real-life “Urquhart Castle” which is close to the village of Drumnadrochit and does overlook the Loch. - Art Shift: Beginning with this title, the direct-to-video Scooby-Doo movies are now designed and animated in a more realistic style again, similar to the first four movies but not as dark and detailed, looking more like something from Adelaide Productions.
- Believer Fakes Evidence: Professor Fiona Pembrook creates a phony monster using a Submarine, and some help from a pair of local pranksters, in order to try and get Sir Ian Locksley to take up the cause again and help her search for the creature. Interestingly, sonar pings from below where her homemade sub could go do get Sir Ian's interest, despite having already been presented with faked evidence.
- Big Shadow, Little Creature: Scooby and Shaggy get scared by the shadow of what appears to be the Loch Ness monster. It turns out to belong to a small salamander, to their relief.
- Bookcase Passage: There's a bookcase that's really a secret passage in Blake Castle.
- Bookends: When the gang first arrive and depart from Loch Ness it is bookended by Scooby sighting something large swimming in the loch.
- Cool Boat: Sir Ian Locksley's got an impressive boat. Professor Fiona's as well if you count the fact that it has a Nessie submarine docked under it.
- "Could Have Avoided This!" Plot: The person behind the fake monster only wanted to try and make Sir Ian believe in a real one, and did the whole scam instead of just showing Ian the very good photos they seem to have of the "real" monster. After the hoax is revealed and they discover that a piece of equipment from Ian's mini-sub that captured something from a depth that would be far too deep for Fiona's homemade submarine, Velma prods Fiona into sharing her photos with Ian... and he's instantly hooked. While he claims that he's still not a full-on Nessie-believer, Fiona's photos are enough to convince him that the Loch Ness Monster might actually exist.
- Creator's Culture Carryover: The Mystery Machine drives past a road sign for the A83 towards Loch Ness. The road number is right — but the sign is an American-style shield, not the road signs used in the UK.
- Dead Hat Shot: After the Loch Ness Monster attacks a boat full of volunteers for the Highland games in the opening scene, a violin that one volunteer was playing ominously washes ashore, while the volunteer himself is nowhere to be seen. However, later comments make it clear that everyone on the boat survived, indicating he just took longer to swim to shore.
- Everyone Is a Suspect: With the exception of Shannon (Daphne's Scottish cousin who's the current owner/primary caretaker for Blake Castle), pretty much everyone that the gang meets while in Scotland has a motive for potentially being behind the fake-Nessie:
- Professor Pembroke would want more people to believe in the monster in general to help her research.In reality she just wanted to make a believer out of Ian, frustrated with his cynicism.
- While he doesn't seem to have a motive, Sir Ian clearly has the funds to create the sort of aquatic machinery needed to fake the monster and shows up very eager to hunt it down.He just wanted to end the hoax and stop the threat to the games.
- Dell Chillman thinks the games are making Nessie angry and causing other problems, so the gang think he may be behind the monster to scare people off. He's not, though his van is stolen and used in the hoax.
- Colin and Angus would want to potentially scare away competition from the games.They don't really care about the games but were involved anyway because they thought it was a good prank.
- Mr. Haggart, Colin and Angus's dad, wants more people to believe in Nessie because it will increase business for his inn.He's not involved with the hoax at all.
- Duncan MacGubbin is cryptically creepy and seems to have some odd warnings about the Blake Castle... nope, he's just a normal (albeit still creepy) guy.
- Everything's Louder with Bagpipes: Naturally, for a film set in Scotland. They show up at the Highland Games at the end.
- For the Evulz: Colin and Angus only help the culprit with their scheme because they think it's a good prank.
- Glamour Failure: The monster that was made out of Dell's van and chased the gang on land goes from terrifyingly realistic like the one in the water to obviously just a cheap costume on a vehicle once the chase scene is over.
- Haggis Is Horrible: Not even Scooby and Shaggy will give haggis a try.
- Karma Houdini:
- Professor Pembrooke commits outright academic fraud, damages a historic castle, delays the opening of the Highland Games, and endangers lives by sinking a boat with people onboard and gets away with no consequences whatsoever.
- Sir Ian's mutinous crewmen are last seen abandoning their ship. The movie novelization mentions afterward there's an APB out for them, but they are still at large.
- Lots of Luggage: Daphne. Lampshaded at the end when the Fred, Shaggy and Scooby are forced to help carry her stuff.Shaggy: Maybe next year there can be an event called "the long-distance Daphne Blake-suitcase carry"!
- Meaningful Name: Del Chillman is a laid-back hippie.
- Monster Mouth: The Loch Ness Monster has a terrifying set of jagged teeth, and the main characters get an unwanted close-up look at them whenever the monster roars.
- Monumental Damage: The monster knocks a tower clean off Blake Castle at one point, with Shaggy and Scooby inside it.
- The Mutiny: Sir Ian's crew turn out to have ambitions of their own and try to catch the monster for themselves, interfering with the gang's trap.
- Mythology Gag:
- The Loch Ness Monster and a spooky castle were previously featured in the The Scooby-Doo Show episode "A Highland Fling with a Monstrous Thing".
- Daphne's cousin Shannon describes the Blake family as being "danger-prone" and having a history of falling into all sorts of traps. "Danger-prone Daphne" is classic in-series nickname due to how often she was captured or trapped.
- Shaggy remarks, "The fog's so thick, you could cut it with a knife," to which Scooby cuts a piece with his claw and eats the piece like a pancake, is an identical gag from the "Go Away, Ghost Ship" episode of Scooby-Doo, Where Are You.
- New-Age Retro Hippie: Del Chillman’s a lot like a hippie.
- Non-Malicious Monster: Ambiguously done with the real Nessie who’s only seen at the end passively swimming alongside the Mystery Machine.
- Nothing Is Scarier: The Wham Shot of Scooby potentially seeing the real Nessie as they drive away from Blake Castle seems to indicate that the gang may have been dealing with the real thing on at least a few occasions throughout the movie. There's no way of knowing which attacks were just staged and which ones were where lives were actually in danger.
- The Prankster: Colin and Angus like to play practical jokes.This is how Fiona got them involved in the plot.
- Real After All: At the end of the movie, when the Mystery Gang is driving off, Scooby notices a large, Nessie-like creature swimming in the lake nearby before diving underwater, leaving him bewildered. It’s possibly the real monster.
- Red Eyes, Take Warning: The monster has red eyes.
- Road-Sign Reversal: When Shaggy and Scooby are driving around in the Mystery Machine, someone pulls the "switch two signs" trick on them, sending them into a swamp.
- "Scooby-Doo" Hoax: Three fake monsters - one that chases Shaggy and Scooby at Blake Castle at the start, and later chases them into a pit (it turns out to be Colin and Angus); Professor Pembrooke's mini-sub that chases them in the loch; and Del's van when it's made out to look like a monster.
- Shout-Out:
- The Loch Ness Monster's design in this film is almost identical to the Paleosaurus. Both films were from Warner Brothers.
- The scene of the gang on a fishing boat against the monster under the water is based off Jaws.
- The monster's huge eye looking into a vehicle's side window is from Jurassic Park.
- Duncan MacGubbin's look is meant to resemble actor Marty Feldman.
- Shown Their Work:
- This is one of the few media depictions to depict the Loch Ness Monster as amphibious rather than fully aquatic. The initial wave of Nessie sightings involved the creature walking along on land or resting on the shores of the lake rather than swimming.
- Sightings of the Loch Ness Monster in water mainly involves the creature's back poking through the surface, with the iconic long neck being attributed to hoaxes. This is reflected by the (possibly) real Nessie in the movie, and it's only natural that the fake Nessies possess the long-necked form.
- Skewed Priorities: During a Chase Scene, where the Lochness Monster chases the Mystery Machine, Fred calls the monster a lizard. After Velma tells him that the monster technically wouldn't a lizard, the monster is actually amphibious, much to the annoyance of Daphne, who lampshades how it isn't the best time to point out that fact.Daphne: Not the time, Velma.
- Stock Ness Monster: It's the real deal. Well, actually, one is a submarine, one's a land-based costume, and a third is Del's van, but there's potentially a real one too.
- Sub Story: The gang travels into Loch Ness in a sub to explore underwater caves.
- Tempting Fate: When Shaggy and Scooby accidentally lock themselves outside Blake Castle.Shaggy: Well, look on the bright side, Scoob. At least it's not raining.
- Walk on Water: Shaggy and Scooby manage to run on water using oars.
- Wanted a Son Instead: After watching his grown sons laughing about their role in a practical joke, the local innkeeper laments that he "should have prayed harder for daughters." The fact that he's a Sports Dad and they don't take take sports seriously doesn't help.
- Wham Shot: The plan to trap the monster in the climax is going well. Then Daphne reaches for her walkie talkie to contact the others and First Mate McIntyre grabs her arm, launching a Spanner in the Works mutiny to try and capture the monster himself and sell it on the black market.
- Why Are You Looking at Me Like That?: When Shannon talks about her family's "danger-prone" history, the rest of the gang glance at Shannon's constant Damsel in Distress cousin Daphne, causing her to angrily say "What?"
