Tigger, Rabbit, Gopher, and Piglet are telling stories on a dark night in the Hundred Acre Wood. Tigger wants Piglet to tell a story about ghosties, spookables and "things that go shopping in the night". But Piglet says he wants to tell a "not-so-scary story" about a scientist.
In the story, Piglet sets the scene in a castle in the middle of the day. Tigger says the story should be in the nighttime, and the day turns to night. Piglet and Tigger go back and forth, changing the story from day to night. Tigger confuses Piglet and the story stays at night. Tigger adds a thunderstorm. Inside the castle, a scientist who looks exactly like Piglet is in a laboratory making a peanut butter and jelly sandwich. Tigger interrupts again and says, "this story is so unscary, it's scary!"
Outside the story, Tigger is fed up with how the story is going and gets up to leave to "go trim Pooh's toenails". Rabbit tries to get Tigger to stay. Tigger says that if the story is going to be about a scientist, then he should be doing something "terribibble," like creating a "boogly, boogey monster!"
In the story, there is something under the blanket on the table the scientist Piglet is working on. Tigger names it The Monster Frankenpooh as it sits up. The blanket comes off and the Monster Frankenpooh looks exactly like Winnie the Pooh. Tigger says the monster is "absolutely perfect," but thinks the monster should be bigger. Frankenpooh suddenly grows bigger, big enough to sit on the table. Tigger is still displeased with the size of his monster, so he makes Frankenpooh even bigger. Tigger wants the monster to be even bigger still, so he makes Frankenpooh so big that he hits his head on the ceiling of the castle. Finally, Tigger is happy with the size of The Monster Frankenpooh. The terrified scientist runs around Frankenpoohs feel yelling for help, and then breaks the fourth wall, saying "this is so very terrifying," before running away. Frankenpooh slowly begins to walk out of the castle, looking for honey.
Outside the castle, Frankenpooh walks through a farmer who looks like Rabbit's garden, and he yells of a monster. Frankenpooh makes his way to Gopher's hole, and walks over it, making Gopher, who also yells of a monster, fall a very long fall all the way down his hole. Tigger appears and asks if the audience is scared.
Outside the story, Tigger says how the "giganticically monstrous monstrosity" is unstoppable.
Inside the story, the giant Frankenpooh walks along, yelling for honey.
Outside the story, Piglet stops the story and tells Tigger that the story is much too scary, and suggests that he take over.
Inside the story, Rabbit and Gopher are running scared around Frankenpooh's feet. Piglet says the size of the monster is all wrong to have on him, and Frankenpooh instantly shrinks back to the small size he was at the beginning of the story.
Outside the story, Tigger agrees with Piglet about the monster's size, and says that the monster should be "quadroopily as big!"
Inside the story, Frankenpooh grows very rapidly, and grows so big that he reaches the top of the film strip the cartoon is being made on. Frankenpooh breaks the fourth wall and comments on his size to Tigger. Tigger agrees that he overdid the size of the monster, and shrinks Frankenpooh back to his original, but still big, monster size. Frankenpooh continues on his way looking for honey. Eventually, he finds a house, sits down in front of it and tries to reach inside it (only being able to fit his arm inside it) to look for honey.
Meanwhile, a trio of angry villagers (Rabbit, Gopher, and Owl) Run to the scientist's castle, claiming that he is the one who made the giant monster. The scientist, who is putting out empty milk bottles, is frightened by the villagers and runs away into the castle, as the villagers chase after. Piglet hides and pleads that the whole thing was an accident.
Outside the story, Piglet is trembling in fear. Tigger, Rabbit and Gopher are confused, and go to comfort Piglet, assuring him that it was only a story and there is nothing to be afraid of. Rabbit says that Piglet should learn the difference between what is real and what is not. Rabbit asks Pooh if he agrees.
Across the room, Pooh is sitting on the ground, but he is the same giant size he was in the story. Pooh also agrees that he shouldn't take things so seriously either.