Mametchi and Chamametchi suddenly switch bodies.
At the Mame House, Mamametchi comes in Mametchi's room and asks him a favor to deliver Papamametchi's lunch. Knowing that he has to go directly to Mamemame Laboratory, Mametchi happily agrees. Chamametchi comes in near the door and asks that she wants to go to the laboratory too. Mametchi paused for a moment, but Chamametchi frantically begs. So Mametchi agreed to let her come.
As the two walk to the Mamemame Laboratory, Mametchi tells Chamametchi that they must focus on delivering the lunch. Chamametchi casually acknowledges him, but diverted her own attention to random sights along the way to laboratory, much to Mametchi's disappointment. Soon as they arrive and enter at the laboratory, they start walking around to look for Papamametchi. While searching around, Chamametchi enters a room and sees a room with a high-tech equipment. Then she starts shuffling around the console. Mametchi comes in to remind her that they need to deliver the lunch. But suddenly, Chamametchi curiously presses a random button on the console that activates the machine in front of them, and a bright flash of white occurs.
Mametchi wakes up. As he tries to wonder what happened as he lays down on the floor apparently unconscious, Mametchi realizes that he's looking at himself in Chamametchi's body. Wondering if it's a clone, it wakes up and spoke in Chamametchi's voice as she wondered what happened after the light, shocking Mametchi. Knowing what happened, Mametchi in Chamametchi's body comes up to a mirror and discovered that he is actually Chamametchi.
Chamametchi, in Mametchi's body, wondered why she became taller, while Mametchi, in Chamametchi's body, tries to make her see the seriousness in their current situation. But Chamametchi was absent-minded at first, seeing Mametchi as a 'clone' and even thinking it's another girl dressed as her. When Mametchi assured what the machine did, Chamametchi believed him. However she was glad of the change with Mametchi's body because she's taller and can jump higher. Mametchi's attempts to make her see reason failed, so he decided that he needs to activate the machine again. Viewing the console, Mametchi tries to think which button to press. He asks Chamametchi to help, and she said it might have been the red button. Mametchi presses it, but Chamametchi makes a late response that it was something after it. Confused at the mishap, the machine flashes another white bright light.
Elsewhere in the laboratory, Mamehakasetchi asks Papamametchi a question if he is working overtime. He responsed he will be going home after processing research on his computer because he forgot his lunch. Humbily acknowledging it, Mamehakasetchi leaves the room hoping to see him tomorrow.
Back at the mind-swapping machine, Mametchi and Chamametchi wake up again after the light. However, they seemed to be in one combined body, where Chamametchi is pondering around where' When Mametchi realizes what's going on, he checked the mirror again and becomes shocked that he and Chamametchi fused together, even calling themselves Mamechamametchi.
Chamametchi skips happily in the fusion exclaiming that she can jump and play freely. But Mametchi urges her that they need to get back to normal right away. Mametchi tries to find Papamametchi for help, but Chamametchi still insists on playing with the fused body. As their two minds continue to clash with each other, Chamametchi fell and hurts herself, then cries over it. Mametchi regains controls of the body and disregards her feelings just to get back to normal. Mametchi heads for the room exit, but discovers that it's locked shut. Chamametchi continues crying, but Mametchi effortlessly tries to calm her down. Then he wonders how will the two can cope in their fused body.
Night falls. Mametchi and Chamametchi are still trapped in the room. They started to feel very hungry. Then, the two realize Papamametchi's lunch lying on the floor. Chamametchi happily wants to eat from it, but Mametchi insists it's supposed to be for Papamametchi. But due to the fact he's starving, he assumes their situation is going to be a long night and agrees to eat it. Unfortunately, the two fight over which sandwich to eat. In spite of it, they were able to sate their hunger. Chamametchi began to feel sleepy afterwards, but Mametchi urges her to stay wake and think of a way out. However Chamametchi went to sleep and eventually Mametchi falls asleep with her.
Then, someone unlocks the exit and it is revealed to be the Spacy Brothers, posing in style as they enter. Akaspetchi worries over if someone catches them sneaking inside Mamemame Laboratory, while Spacytchi tells him that the laboratory is full of machines they can use for their world domination. Pipospetchi then points out to the same console in the room. Spacytchi heads over it and thinks it might help them in their conquest. Akaspetchi becomes cautions, but Spacytchi says he knows how to work machines. But before he could act, Pipospetchi presses a random button on the console. Spactchi remarks on him for going ahead of him, but then the mind-swapping machine activates and generates another flash of white light.
Mametchi wakes up again, being aware he felt the machine's swapping sequence. But when he looks at his hands, he becomes relieved he is finally back to normal. He then comes up back to the normalized Chamametchi and wakes her up. Awakening, Chamametchi began to feel she got small again. Mametchi tells her that they're both back to normal again, but Chamametchi was disappointed since she finds it exciting. Them Mametchi wondered how they were back to normal, then he spots the unlocked exit door, opened earlier by the Spacy Brothers. Great to see that the way out is clear, Mametchi and Chamametchi walk back home together.
Back at the Spacy Brothers, Spacytchi wakes up in Akaspetchi's body, wondering what happened. Akaspetchi wakes up in Pipospetchi's body wondering with him, surprising Spacytchi on how Pipospetchi finally talks. Akaspetchi said to him that he can see himself and that Spacytchi's body is lying down on the floor. Spacytchi becomes confused, and asks for Akaspetchi's identity. He verifies that he is Akaspetchi, but Spacytchi only sees Pipospetchi. Pipospetchi, in Spacytchi's, wakes up after hearing his name to respond back, eventually the two realize they all switched bodies.
Outside the Mamemame Laboratory, Mametchi sees that's it's already late and suggest the two take a shortcut. Chamametchi delightfully goes along with Mametchi's suggestion. At the Spacy Brothers once more, Spacytchi says that his world domination plans have been ruined, Akaspetchi thought they pressed the wrong button, while Pipospetchi ask what, freaking the two out.