A giant caterpillar arrives in Cappy Town and makes everybody sick with hay fever. When the caterpillar makes a cocoon, King Dedede tries to burn it. It doesn't end up growing, but instead develops.
Spoiler alert: The following section contains plot-specific details.(Skip Section)
On an island in the middle of the ocean, two sisters are singing on a flower in harmony. While this is happening, a giant caterpillar is feeding on the local trees and listening to their singing. When the the sisters finish their song, the sky mysteriously turns dark and a giant hand grabs the sisters. When the caterpillar realizes they're gone, he lets out a cry.
Meanwhile at the castle, when King Dedede wonders why no one is on duty, he finds the Waddle Dees sneezing. He goes to Waddle Doo and asks why no one is working. Waddle Doo tells him that 'the Waddle Dees all have stuffy heads'. Escargoon comes in saying he has a head cold too. After he is told this, Dedede wonders why he is not sneezing. Escargoon suggests that the sickness may be a cold, but then he sneezes into Waddle Doo.
End of spoilers
Changes in the dub
Inside Chef Kawasaki's restaurant, several kanji on the wall were airbrushed out.
In the Japanese dub, the pollen that the mayor and Chief Bookem observe in the microscope was moving in random directions. In the English dub, the pollen does not move, for unknown reasons.
The scene where the Waddle Dees are trying to catch up with King Dedede from a long distance was removed from the English dub, likely due to time restraints.