Helen, Alice, and Martha are running to an annual used book sale at the library, but unfortunately Truman has already beat them to it and bought all the good books, the way he does every year. However, he lets the girls look through them and see if they want to borrow them.
While the girls are looking through Truman's books in the Oatley garage, T.D. shows up, disappointed that the only book at the sale was a boring one on grass. Truman lets him join in on looking through the books, and as the four of them are looking, Ronald bikes up. He wants to read a sophisticated book, so Truman hands him a textbook on psychology, and he bikes off with it.
At breakfast in the Boxwood house the next morning, Ronald is reading his psychology book, when Alice tells him to pass the jam. He asks if she wants grape or strawberry, but she says it doesn't matter. Ronald then messes with Alice by saying that according to his book, her inability to decide which jam she wants means she's not right in the head and has a bad case of "decidophobia". Later, Alice is hanging out with Helen, who asks her which of three of her books she borrowed Alice wants to read first. Alice, however, is still reeling from what Ronald said, so she runs home screaming.
Helen later comes to the Boxwoods' with Martha and Skits, wanting to play with Alice in the park. However, she finds Ronald instead, and when she asks if Alice is okay (wondering why she screamed earlier), Ronald decides to mess with Helen too by pretending to diagnose her with "worryitis". He claims that this is a serious psychological condition characterised by worrying too much, and points to her fear of Skits swallowing a rock as evidence of the alleged diagnosis.
Later, Ronald comes over to the Oatleys' house, where Truman is organising his books. Ronald thanks Truman for lending him the psychology book and asks for more psychology books. Truman says he won't know until he's done alphabetising his books, to which Ronald claims that his book says that Truman's alphabetising his books means he has "arrange-o-mania", a condition in which one becomes too focused on perfecting one thing and forgets about everything else. Truman remembers that he let his grilled cheese sandwich go cold when arranging his books and decides he must have that condition.
That night, Alice is still concerned that she really does have "decidophobia" when she can't make up her mind what pyjamas to wear, and Helen fears that she really does worry too much, not helped by Martha saying, "You sound worried" when asked about it.
The next day, T.D. meets Alice on the sidewalk, who can't decide if she should jump over a mud puddle or go around it or whether to have pudding or yogurt for dessert, so he tells her to jump and have yogurt. He then returns the book he borrowed to Truman, who asks T.D. how much time he spends on organising things. T.D. says he spends no time doing that, and borrows another book.
Helen and Martha then take a walk, both convinced that they have "worryitis" — Helen because she worried about Ronald's "diagnosis" at night and Martha because she fears she's not getting enough bacon. She meets T.D. at the corner store, now reading a different book and not caring that his shirt is on backwards. Later, Martha meets Alice, who is now wearing a different outfit and reading a book without her glasses. She then meets Truman, who has decided to start collecting "junk", and wants to borrow a book on bacon. However, he reveals that he mixed his books in with his junk collection.
At the park, Martha tells Helen (who is reading) about how strangely Alice and Truman were behaving oddly, but then Helen starts behaving oddly too — she's wearing her shirt backwards and claiming she wants to have books that can be read via smell. Truman, T.D., and Alice walk up, also reading, and then whenever T.D. does something, Helen, Truman, and Alice start copying him. Martha says, "You're all T.D.!", and the other kids admit that they've been emulating him. Martha asks them why, feeling that this makes no sense.
At the corner store, Alice reveals that the reason she's been copying T.D. is because of Ronald's "diagnosis". Helen says that decidophobia doesn't sound too bad compared to worryitis, which is what Ronald diagnosed her with, but Truman doesn't believe such a condition exists. He adds that Ronald "diagnosed" him with "arrange-o-mania", but he's not so sure now. When all the kids get given seaweed-flavoured yogurt, which only T.D. likes, Truman decides to get a dictionary.
At the Boxwood house, Helen, Alice, T.D., and Truman confront Ronald and claim to want the psychology book back, wanting to read about their "conditions". They reveal that they've looked them up in the dictionary, which claims that there's no such thing as "worryitis", "decidophobia", or "arrange-o-mania", and they force him to confess that he made the conditions up and never even read the book. Then, T.D.'s friends decide to go back to normal.
This episode provides examples of
- Alliterative Title: Not the episode title, but one of Helen's books is called The Creepy Carnival Caper.
- Collective Death Glare: Martha, Helen, Alice, T.D., and Truman all glare at Ronald for lying to them.
- Collector of the Strange: Truman decides to start collecting "junk" in this episode.
- Continuity Nod: When Truman reveals that he's started collecting junk, Martha replies, "Like T.D.?". T.D. collected junk in "T.D. the Pack Rat" (and presumably still does, but he donates his collections to the junkyard now).
- The Ditherer: Discussed when Ronald claims Alice's not caring what flavour of jam she wants means that she's bad with decisions in general.
- Dogs Love Fire Hydrants: One of the things Martha likes sniffing at is a fire hydrant.
- Eat Dirt, Cheap: Defied when Helen swipes a rock from Skits so he won't swallow it.
- Entertainment Below Their Age: Defied. Ronald refuses to read any children's book, since he thinks they're "for babies".
- Extreme Omnivore: When Martha says she loves to eat grass, Truman claims he does too.
- Facepalm:
- Helen puts her palm to her face when confused by T.D. liking a book on seaweed despite disliking a book on grass.
- Later, Alice does the same after stepping in a mud puddle.
- Fun with Homophones: T.D. sees a book about hay and yells, "Hay!". Truman thinks he said, "Hey".
- Hidden Depths: This episode reveals T.D. to be interested in moss, hay, and seaweed.
- Incredibly Lame Fun: The girls are weirded out by T.D. enjoying a book about seaweed.
- Insane Troll Logic: T.D. dislikes reading about grass, but likes reading about seaweed, despite that being essentially just sea grass.
- Irony: Helen decides she really does worry too much when Martha observes that she's worried, even though Helen was only worrying because Ronald put the idea in her head.Helen: "Oh my gosh! I'm worrying that I'm worrying!"
- Nature Lover: Zigzagged. T.D. is revealed to like reading about some plants, but not grass.
- Nervous Wreck: Discussed when Ronald claims that Helen has "worryitis"; a psychological condition that manifests as excessive worrying.
- Non Sequitur: When Helen claims not to be worried about Alice and Truman's strange behaviour, she says, "Wouldn't it be great if there were books you could read just by smelling them?". Moments later, T.D. thinks the same thing.
- Only One Who Likes Spam: T.D. is the only one who likes the seaweed yogurt.
- The Perfectionist: Discussed when Ronald claims Truman is "too focused on getting one thing perfect", referring to his alphabetising his books.
- Running Gag: Martha keeps wanting a book on bacon (she can't read, but presumably she wants Helen, Danny, or Mariella to read it to her).
- Somethingitis: When Helen asks if Alice is feeling okay, Ronald pretends that this means Helen has "worryitis".
- Speak in Unison: When T.D. says something while Helen, Alice, and Truman are copying him, they reply in unison.
- Strange Minds Think Alike: Helen and T.D. somehow both separately come up with the idea that it would be great to have books that could be read by smell.
- Sweet Tooth: Alice is revealed to like strawberry jam, grape jam, pudding, and yogurt equally, and she's also shown enjoying a stack of pancakes.
- Unwitting Instigator of Doom: Truman accidentally causes himself and two of his friends to worry needlessly by lending Ronald the book on psychology, which he uses to mess with the kids.
- Why Did It Have to Be Snakes?: Discussed when Ronald tricks Alice into thinking she has "decidophobia"; the fear of making decisions, just because she was indecisive about her jam.
