The Magic School Bus in the Haunted House
The episode opens with soft music playing over the opening shot before the scene quickly changes over to outside of the school and a change of music to something louder and much faster paced. Inside the classroom, it turns out to be the piece that Ms. Frizzle's class is playing for a concert the next evening and the kids are practicing in the classroom with Dorothy Ann being the conductor and the other kids each having an instrument to play. Every instrument is normal, except for Carlos's instrument that he made himself. When Carlos plays his part of the piece though, it sounds "ploopy" according to Ralphie. Carlos wonders what he did wrong.
Ms. Frizzle then walks into the classroom, while playing a drumset. She asks Dorothy Ann if the music playing was her piece, to which D.A. responds that it is. She and Carlos then explain the problem with his instrument but that there's no time to fix it before their rehearsal that night and the concert that will be at the sound museum the following night. Ms. Frizzle explains to Carlos that if he keeps asking questions, he will get answers.
"But there's no time for questions, Ms. Frizzle!" Dorothy Ann tells her, as the class needs to hurry to get to their rehearsal on time. Ms. Frizzle then gets the class to get on the bus as "those who are great are never late". That however turns out to not be the case as the bus breaks down part of the way there due to overheating. All the kids (minus Carlos) decide to push the bus while Ms. Frizzle pulls it along the road while Carlos tries to work on his instrument. Carlos adds various odds and ends to it, but it only sounds worse and worse.
Suddenly, a strange and eerie sound fills the night. The others think he's finally got it, but he points to what appears to be an old abandoned house and they decide to go investigate. Once they are inside, the door closes behind them by itself. Naturally, the kids are freaked out. Ms. Frizzle then sees a portrait of the home's former owner, Professor Cornelia C. Contralto, an eccentric sound collector who lived during the 1800s. She then explains that Professor Contralto's home, where they are now, was turned into the sound museum (thus putting the class where they intended to go). Dorothy Ann then realizes that they've missed the whole dress rehearsal and Ms. Frizzle explains that since everyone else has gone for the night, they've got the whole place to themselves.
As the whole class walks down a spooky hallway and Ms. Frizzle explains how Professor Contralto dedicated her life to sound, Tim sees the eyes of a portrait of the professor moving and gets freaked out:
Tim then discovers a passageway into a bedroom that is set up with 8 beds for the students. The students are told to get some rest for the concert tomorrow but everyone is too scared to sleep. Carlos then adds a sheet from one of the beds to his instrument to try to make it sound like a ghost, much to Dorothy Ann's annoyance.
Carlos then decides to ask the ghost of Professor Contralto for help. Shortly after, the class hears the strange noise that they first heard when they arrived. Carlos is sure that this strange sound is what he dubs "the call of Cornelia" and decides to find out what's making said sound. The kids and Liz, not wanting him to go alone, follow after him. They soon find that they're getting closer to the sound as it's getting louder.
They then hear the sound of someone yodeling and go into a room that has scenery from a jungle, a beach, a city, and an alpine wonderland. Tim comments on the weirdness of the house and the kids soon discover that it was Ms. Frizzle who was yodeling. Carlos then hears the "call of Cornelia" again and asks how to get out of the room they're in. Ms. Frizzle declares that the only way out is up so the class rides a ski lift before being dropped through a funnel into a room with giant musical instruments.
The class then learns that it's something vibrating that makes a sound. Carlos then realizes that he has to make his instrument vibrate. They then move into an auditorium and Ms. Frizzle, Liz and the kids each get a set of magic glasses in order to see sound. They then learn the difference between higher pitched and lower pitched sounds.
Carlos, realizing it doesn't matter how his instrument looks as long as it can vibrate, goes to get his instrument from the bedroom but discovers that it's gone and then they hear the strange sound form earlier again and Carlos jumps into a basement, realizing the sound is coming from there. Ms. Frizzle, the other kids, and Liz jump down after him (though Arnold is reluctant to) and go down a hallway to find the sound now that they have an idea of where it is. They go through a door and discover a woman playing an organ and find out that she is Professor Cornelia C. Contralto II, great-great-grand daughter of the original Professor Contralto.
Professor Contralto II then asks Carlos is he's ready to make his instrument sound good (with Ralphie wondering how she knew about this). Carlos takes several things off his instrument in order for it to sound better, finally understanding the concept of sound and how it's made.
The next evening at the concert, the kids perform their piece and Carlos' instrument works perfectly, which causes them to get a standing ovation. Dorothy Ann hugs Carlos, declaring that it was the perfect sound and as the curtain closes, Professor Contralto II asks Carlos if she can add his instrument to her great-great-grandmother's collection. Carlos says yes.
The main episode ending has Ms. Frizzle and Professor Contralto II singing the "high-di-high-di-high-di high/low-di-low-di-low-di low" song that was sung earlier by Ms. Frizzle to teach the kids about higher and lower sounds and the kids laugh; the camera then briefly focuses on the outside of the sound museum before the screen fades to black.
- Sound travels too fast to be seen, as pointed out by the caller (hence the magic glasses)
- Vibrations are made by pushing something back and forth on the air, creating sound.
- A brief explanation on how hearing works when the caller mentions that how ears work wasn't really talked about in the episode and about her grandmother having to wear a hearing aid. It is then explained by the unseen receiver of the call that some suffer too much hearing loss to be able to hear even with a hearing aid and have to use their other senses to replace hearing.
- The caller points out there are other differences between sounds beside loudness and pitch. The receiver of the call confirms this and explains that they only had half an hour and had to leave room for the jokes.
The caller then points out that the ghost the kids thought was around couldn't have actually been there since "everyone knows there's no such thing as ghosts."
"Of course not," the receiver of the call replies, as the chair turns around while Liz is on one armrest revealing that it was a ghost answering the phone. Said ghost laughs evilly while Liz runs out of the office, completely terrified at this revelation.
- Arbitrary Skepticism: Averted. Contrary to a later episode, the class doesn't express disbelief when Ralphie brings up the possibility that the house is haunted. No one also questions the portraits of Cornelia the First that wave to them.
- Arc Words: "If you keep asking questions, you keep getting answers."
- Bait-and-Switch Comment:Wanda: Come on, you weasly wimps! (scared) Let's follow Miss Frizzle.
- Bizarrchitecture: Much of Cornelia C. Contralto's house, with the ear and bat decorations on the outside to the city/jungle/beach/Alpine wonderland room.
- Bookcase Passage: More accurately a Fireplace Passage, when Tim steps on the panel in front of the fireplace the wall rotates around to the guestroom.
- Cobwebs Of Disuse: There's quite a few in the front room of the house.
- Cool, but Impractical: What Carlos realizes about his instrument; adding stuff to it looks cool, but the sound becomes even worse with each addition.
- Dramatic Thunder: Played straight frequently during the haunted house scenes. Initially, the thunder Stock Sound Effects used are the "Castle Thunder" sounds used by Disney and Hanna-Barbera (like many of the show's sound effects are), but halfway into the episode it inexplicably switches to more newer realistic and loud thunder crashes. Then it goes back to "Castle Thunder" for the Producer segment.
- Faking Engine Trouble: When Carlos needed some more time to perfect his music instrument, Ms Frizzle overheated the bus's engine to buy some. It's unclear if she actually overheated it or if she just said it was given the bus winked at her as she was checking it.
- Gadgeteer Genius: Carlos made an instrument that when played right sounds like a xylophone, pipes, and a cymbal.
- Ghost Butler: When the class first enters the house, the door closes on its own, freaking Arnold and Ralphie out. Then the door won't open...
- Give Me a Sign: Carlos as the kids are going to bed asks for Cornelia's ghost to help him. Then he hears the pipe organs and decides to follow "the call of Cornelia".
- Haunted House: Where most of the episode takes place (with the exception of the first scene)
- Hell Is That Noise:
- Every time Carlos's instrument plays, before he fixes it. EVERY TIME.
- The pipe organ themes that keep playing.
- The yodeling echoes, which turn out to be Ms. Frizzle.
- Hidden Depths: Apparently the whole class can play the "William Tell" overture with perfect intonation, and DA is a master conductor.
- Meaningful Echo: "You asked a question!"
- Mickey Mousing: The eight beds made up for the class light up one-by-one in time with an eerie c-minor scale.
- Nothing Is Scarier: The producer in the post-episode sequence is revealed to have been an empty chair, most likely a ghost.
- Ominous Pipe Organ: Heard throughout, and alarms the kids but it's really just Cornelia C. Contralto the Second.
- O.O.C. Is Serious Business: Carlos makes less puns in this episode than he does in the others because he's too worried about his instrument.
- Perfectly Cromulent Word: Apparently "ploopy" is a good way to describe Carlos's sound.
- Portrait Painting Peephole: The eyes in Cornelia C. Contralto's portrait move.
- Rule of Three: After the bus breaks down (and while the rest of the class is pushing it while Ms. Frizzle pulls it) there are 3 different times that Carlos adds something to his instrument to try to make it sound like a certain thing. The first two times (after trying to make said instrument sound like a thunderstorm and a cat, respectively) Dorothy Ann tells him it sounds like a drizzle and the second time, like a kitten. The third time before Carlos can ask again, the class tells him "Forget it, Carlos!"
- Running Gag: Carlos's instrument making a "ploopy" sound.
- Special Guest: Carol Channing voices Professor Cornelia C. Contralto II.
- The Un-Reveal: Although it turns out a real person was playing the pipe organs, the episode never explains why the portrait of Cornelia C. Contralto the First has moving eyes and can even wave to Ralphie and Carlos. The Producers segment makes it more blatant that ghosts are involved.
- What Happened to the Mouse?: In-universe, Tim asks what happened to Cornelia the First. Ms. Frizzle ominously replies, "no one knows".
- You Were Trying Too Hard: As it turns out, the problem with Carlos's instrument. He was adding so much stuff to it that was messing with the vibrations that it ended up creating a "ploopy" sound. Once he strips his instrument to the bare minimum, it plays perfectly.