It's Halloween, and Adam Lyon is seen walking to Charles Darwin Middle School in a pirate costume, complete with a fake parrot on his arm. Adam's really excited for Halloween, and as he's walking to school, he hears the howling of animals, and assumes that his animal classmates are excited for Halloween.
When he walks into school, he sees his best friend, Jake Spidermonkey, and one of his other best friends, Windsor Gorilla, howling at each other. They see Adam in his pirate costume, and wonder why he's dressed up. Adam explains to them how humans traditionally dress up in costumes, while Jake and Windsor explain to him that animals celebrate "Howl-o-ween" by howling all day. Also, Jake mistakes the fake parrot on Adam's arm for an actual parrot, and also thinks that the "parrot" is trying to replace him as Adam's best friend.
Adam quickly gets annoyed with all the howling that the animals are doing, and Jake eventually gets into a fight with Adam's fake parrot, and becomes Adam's new parrot, even assuming a parrot-like appearance. Eventually, Principal Pixiefrog announces over the loudspeaker that he needs a student to go down to the nearly silent boiler room to retrieve a file for him. Adam immediately volunteers for it, and he and Jake go down to the boiler room. As they're climbing down the stairs, one of the steps breaks, but Jake manages to save Adam before he falls, and Jake is---rather surprisingly---flying, but when he stops flapping his arms, he falls to the floor of the basement.
As they're walking through the boiler room, trying to look for the file cabinet, but Adam ends up losing Jake. At first Adam thinks that Jake's trying to scare him, but then Adam gets super freaked out and starts running, and ends up running into the filing cabinet and ripping his pirate shirt. Jake pops out of one the drawers, and reveals that he found the file Principal Pixiefrog was looking for. The boys then hear a noise, and see an elderly man in a custodian's uniform. The man introduces himself as "Old Joe," the CDMS-custodian. Adam's surprised that there are other humans at CDMS, which is an all-animal school, and Old Joe explains that he's been working at the school ever since it was originally a school for humans.
Adam and Jake try leaving, but Old Joe tells them that he wants to tell them a scary story. He tells the story of The Haunted Locker: two students who're very similar to Adam and Jake are walking down their school hallway to their locker, but when they get to the locker, they hear strange noises coming out of it. The boys are scared, but they have to open the locker because their books are in it and the bell's about to ring for class. One of the boys slowly turns the combination on the lock, and when the door opened, the rotting corpse of the school principal fell out. Joe expects Adam and Jake to be scared, but they're not. He doesn't get why they don't find corpses scary. Adam explains that it's not that corpses aren't scary, there just wasn't any build-up to his story.
Joe tries telling them another story, this time about a teen couple making out on Lovers' Lane, but Adam and Jake have already heard the story. Joe then tries telling them a story about a soda bottle with a dead mouse in it, but Jake had already heard the story ("The lady sued the cola company and got millions of dollars. I know 'em all Old Joe, just bring 'em on!," Jake says). Joe tries telling them various other scary stories (Hook Hand, Fork Tongue, Claw Toe, Donut Head, Can of Beans for a Brain) but Adam and Jake have already heard all those stories.
Old Joe tries one last attempt to scare Adam and Jake. Joe sits on a chair, and his head and all his limbs fall off his body. Surprisingly, Adam and Jake still aren't scared. Principal Pixiefrog pops out of the torso of Old Joe, showing it's actually a costume (also showing the whole thing was just a Halloween prank by him). He gives up trying to scare Adam and Jake, but---surprisingly---when the boys see it's their principal, they get totally freaked out and run upstairs to the main floor of the school.
Principal Pixiefrog (who was helped out by Mrs. Warthog) is glad that he was finally able to scare Adam and Jake. But then they hear a noise and get scared, and it turns out that it's the ghost of the real Old Joe, who starts sweeping up the limbs that had fallen from the Old Joe-costume.
|Nika Futterman||Adam Lyon|
|Tom Kenny|| Jake Spidermonkey|
|Rick Gomez|| Windsor Gorilla|
|Maurice LaMarche|| Principal Pixiefrog|
|Grey DeLisle||Mrs. Warthog|
- The title is a pun on the classic Peanuts Halloween special "It's the Great Pumpkin, Charlie Brown".
- Old Joe's story strongly suggests that CDMS used to be a human school, but since he was completely fake, it's most likely his whole story was fake too, and nothing about it was to be taken seriously.
- Running gags include people calling Adam's costume a blouse, Jake assuming Adam's toy parrot is real, and when encountering Old Joe, Jake telling Old Joe that his breath stinks.
- Main characters Slips and Lupe appear in the background, but don't speak. Ingrid doesn't appear at all.