In the Cosy Room, Four and Five are taking turns with play tiles, while a curious Three watches. They end up building a person, and are impressed with it, but Three thinks Four should've been more creative rather than copying Five's side. She demonstrates different positions, such as waving and dancing, that Four could have done with the pretend person, but Four is grumpy and maintains that he likes its uniform look. Three begins dancing around, but accidentally takes the "person" apart. Four is distraught, but Five maintains her optimism: seeing as Four's side used to match her own, they know how to rebuild it. They do so, and then the alarm sounds off.
Agent 17 reports that a boy is trying to make a card, but one side is growing longer. Meanwhile, another boy's dad is trying to cut a cake in half, only to have half of the cake grow bigger. Four is launched and lands on a brick wall.
Agent 22 reports that a builder is having trouble with his piece of wood: it's growing extra pieces, and when he saws them off, more pieces grow. The agents point out a pattern: these things should match, but they don't. Then, the Shape Japer flies into view and Four gives chase.
In a building, a man suddenly grows a third arm and accidentally hits another man. Then, he grows a third leg. Five imagines some glasses becoming lopsided, the Dancing Cow growing an extra horn and all her legs being on one side, and a butterfly being given lopsided wings.
Three calls Eight over to help (because both of his sides match) and starts up the brain gain machine. Eight creates brain gain to correct everything (and everyone) but unfortunately continues to make brain gain after the problems have been solved, which causes Four to be symmetrical and cause the man to have his legs unable to move separately, so he falls over.
Seven shows up (because her sides are different) and makes brain gain that ends up correcting Four and the man. Then, to defeat the Shape Japer, Seven and Eight use brain gain to make the Shape Japer's sides switch between matching and not matching.
Four comes back, they recap the mission, and then back in the Cosy Room, Three observes that Seven's sides don't match but Eight's do. Four asks the viewers (who he erroneously refers to as the agents) which numbers have matching sides and which don't.
This episode provides examples of
- Body Horror:
- The Shape Japer gives a man an extra arm and leg, which stick out like poles. Later, he's rendered unable to move his legs separately.
- Five imagines the Dancing Cow with three horns and all the legs on one side.
- The excessive brain gain ends up resulting in Four having an extra sticky-out bit.
- The Shape Japer is defeated by making her sides alternate between matching (where she looks normal) and not matching (where she has a huge lump on one side).
- Gone Horribly Right: Eight ends up making too much brain gain, which results in things matching on both sides when they shouldn't.
- Happy Dance: When the man is finally cured of his strange physiological changes, he dances around with joy.
- Mirthless Laughter: After Four makes the man's legs not able to move properly, the Shape Japer laughs, "Ha ha ha ha ha!" with a Mocking Sing-Song inflection.
- Slapstick: When Five imagines the Dancing Cow with all the legs on one side, the cow falls over with a wacky sound effect.
- Vertebrate with Extra Limbs: The Shape Japer ends up giving a man a third arm and a third leg.
