While on a boating trip, the gang crash onto Haunted Isle and go searching in the ancient Vasquez Castle for help.
This episode includes examples of the following tropes:
- Affably Evil: After the Vazquez castle ghost is revealed to be an ex-illusionist Bluestone the Great, rather than giving a You Meddling Kids speech, he actually manages to be gracious enough to give an encore performance showing how he managed the intangibility illusion and is quite cooperative when the police take him away.
- Bedsheet Ghost: The Phantom of Vasquez Castle. He has the ability to float around and go through walls non-stop, making his simple disguise scarier and more effective.
- Deadly Euphemism: Upon confronting the gang, the phantom declares that they will "pay" for not leaving. Shaggy jokingly pulls out some coins, but Fred says that that isn't the kind of paying the ghost means.
- Early-Installment Weirdness:
- When Daphne is separated from the gang, she’s shown to be quite independent: she successfully navigates the castle and later arms herself with a vase to attack someone she hears coming toward her. Later episodes would have her as a straight-up Damsel in Distress who ended up Bound and Gagged more often than not.
- There's also the fact that the villain isn't a suspect seen earlier, but instead a random criminal with no connection to any local mystery.
- Expospeak Gag: Velma translates her own fancy talk in a joke at the beginning.Velma: When the barometric pressure dropped and the warm offshore air came in contact with in an inland cold front, we ran into some unnavigable nucleation.Fred: You're right, Velma, whatever you said.Velma: I said, we're lost in a fog.
- Foot Bath Treatment: Scooby uses a foot bath (and a blanket) to pretend he's got a cold so he won't have to sniff out the Phantom. Naturally, the humans don't fall for it.
- Haunted Castle: The old Vasquez Castle, where the gang ends up stranded.
- Human Disguise: The gang attempts to pass off Scooby-Doo as a human when using him as the bait to trap the Phantom, by dressing him in a trenchcoat, a bowler derby hat and a fake mustache.
- Hypocritical Humor: At one point as Scooby and Shaggy are wandering the Vasquez Castle together, they are both whistling to try and calm themselves down, but then Shaggy stops and tells Scooby, "Stop that whistling! You make me nervous!"
- Instantly Proven Wrong; When Velma mentions how she once read that the castle is filled with booby traps, Daphne tells her that only happens in movies. Daphne is then proven wrong when she falls down a trap door.
- Joke and Receive: Shaggy jokes he is so scared that he could eat a ham sandwich; the ingredients needed promptly appear floating in midair. He constructs the sandwich, then says "If only my imagination could cut it in half." Cue a suit of armour dropping its axe and slicing it in two, scaring him in the process.
- Monster of the Week: The Phantom of Vasquez Castle.
- Name Drop: To build up Scooby's courage when using him as bait, he's told to imagine himself as Rin Tin Tin, Lassie, or John Wayne. The last one is what does it for him.
- Nutritional Nightmare: In the opening scene, Shaggy prepares a double-triple-decker sardine and marshmallow-fudge sandwich, complete with an olive on top. But Scooby-Doo ends up eating it before Shaggy can take a bite.
- Real After All: Upon learning that Bluestone was after a hidden treasure rumored to be on the island, Scooby rushes offscreen, as if he's found something. Later, Shaggy wonders aloud if the treasure might be real, and the gang notices Scooby eagerly digging on the beach...and then it's subverted when the only thing he finds is an angry gopher.
- Saw a Woman in Half: Shaggy appears to fall victim to this, with the saw working on its own into the box. But when Velma rushes to the rescue it's too late... only it turns out Shaggy's head in one half of the box is just a dummy head in Shaggy's likeness, and Shaggy is still in one piece cramped up inside the other half.Velma: Hey! This is just a dummy head!Shaggy: (popping out of his half of the box) Someone mention me?
- Skewed Priorities: After a suit of armor seemingly comes to life to chop a sandwich in half (and the sandwich itself floated down from the ceiling), Shaggy and Scooby immediately go running in the other direction—but not before Shaggy turns around to bring the sandwich along.
- The Snack Is More Interesting: Shaggy says he's craving a ham sandwich, and one floats over to him and so does a jar of mustard when he claims he wants mustard on it too. He doesn't seem the least bit confused as to why a sandwich and mustard jar are floating, dismissing everything as imagination.
- Stranger Behind the Mask: Unlike many traditional Scooby-Doo mysteries, the villain under the ghost/monster costume is someone the gang had not met before The Unmasking— in this case, ex-magician Bluestone the Great. The police officer that comes to rescue the kids recognizes him and fills in the gang on who he is.
- Tempting Fate:
- Daphne dismisses Velma's statement that old castles tend to be filled with traps, saying "That only happens in movies!" As she finishes that sentence, she tumbles through a trapdoor.
- A more lighthearted version occurs when a frightened Shaggy wishes he had a ham sandwich—prompting one to float down from the ceiling. He then realizes it needs some mustard—and down comes a mustard jar. For a third request, he asks if the sandwich can somehow be cut in half...and this time, a nearby suit of armor lowers its ax to do just that.
- They Wasted a Perfectly Good Sandwich: Subverted with the sandwich described above—even though a ghostly suit of armor chops it in half, Shaggy takes the time to go back for it after he and Scooby run away.
