Mametchi and Chamametchi are watching an episode of the Gotchiman television show where Gotchiman is walking through a flowery field when a strange glow appears in the sky. Mametchi and Chamametchi then notice a similar glow outside their house and tell Mamametchi about it. However, it's actually Papamametchi, who now looks like Mamametchi because of an alien changing his appearance.
When Mametchi and Chamametchi go outside, they find that a corn-shaped spaceship has turned literally everybody besides them into Mamametchi. To distinguish which one is really Mamametchi, the two try to guess from silhouettes who is who; the fake Mamametchis are all holding items that would be characteristic of other Tamagotchis they know (such as Kuchipatchi with donuts and Flowertchi with flowers), making this one easy.
They then have to guess by the bento boxes the Mamametchis made which one is who. Mametchi guesses the one with the Gotchiman bento is the one they're looking for, but it turns out to be the actual Gotchiman; the real Mamametchi made them a corn cob and gets angry that they don't care about the food she made them, growing in size to the point that she consumes the entirety of Tamagotchi Planet in her anger.
Mametchi and Chamametchi wake up, revealing the previous events to be a dream. When Mamametchi makes a strange comment and serves them corn, the two freak out and wake up again, revealing that was a dream as well. When Mamametchi serves them sandwiches instead, the kids are delighted.