Calvin and Hobbes play football, but soon switch to Calvinball. Socrates comes by, informing the two of a circus truck coming by. Hobbes voices his disgust with circuses, and they resume their game. They find a bunch of circus trucks coming around, and one hits a hole in the road, dropping a box. Calvin examines it, noting that it says "WARNING! MONKEY! DO NOT OPEN THIS BOX!"
Calvin concludes that the box contains something monkeys aren't supposed to see, and Socrates convinces him to open it. It scares off Moe and his Gang of Bullies, and Hobbes is nervous about it.
Unsurprisingly, the monkey (apparently named Monkey) starts wreaking havoc on practically every character. Calvin finally stops it by giving it a ton of bananas.
- A Dog Named "Dog": Monkey.
- Author Catchphrase: "Help. Cry for help." makes a reappearance here, after Calvin and Hobbes III: Double Trouble and "The Black Turning Funnel Part 1" - this time, Hobbes says them after meeting the monkey.
- Balloon Belly: The monkey, after finding the banana pile.
- Call-Back/Mythology Gag: A reference to an early strip is worked in early on and near the end.
- Comically Missing the Point: Twice in a row!Calvin: Well, Hobbes, do you know what this means?
Hobbes: No ice creme?
Calvin: Well, yes, but do you know what else it means?
Calvin: It means that circus trucks are now using phony imposter ploys to get us out here! We should sue them!
- Hypno Fool: A variant - all Calvin has to do to freak out Moe is make some monkey sounds.
- Insane Troll Logic: How Calvin deduces the contents of the box.
- Maniac Monkeys: The episode revolves around one.
- Medium Awareness: Akin to "The Case of the Rogue Water Balloon", Calvin demands that Hobbes not use four-letter words. His next few lines are all four-letter words, and Calvin takes notice.
- Noodle Implements:Calvin: Wonderous idea, Hobbes! I'll go get the flags, wickets, masks and Mom's eggplant casserole.
- Running Gag: "Hasp".
- Sesquipedalian Loquaciousness: Invoked by Calvin:Calvin: Well, I've never heard of [the word hasp], and I don't like you using big words around me!
Hobbes: It's not a big word, Calvin. It only has four letters.
Calvin: Right. And I've warned you about using four lettered words, Hobbes. For you see, four letter words are casual, and unsophisticated! If we want to sound sophisticated, we must not use four lettered words! Am I making myself clear?
- Static Electricity: Socrates calls Calvin "Static Electricity Lad". Calvin resents it.
- Schmuck Bait: In-Universe - "DO NOT OPEN THIS BOX!".
- Shout-Out: The "hasp" debate is a reference to Hank the Cowdog.
- "HEY CURIOUS GEORGE! WE GOT A SNACK FOR YA!"
- Twitchy Eye: Monkey gets one when it sees the pile of bananas.