When Klaatu, Barada and Nikto went on vacation to Earth, Nikto forgot the toy. Later, the Earthlings construct a reactor above, causing the toy ro risk meltdown, causing destruction of all lifeforms on Earth.
Klaatu, Barada and Nikto fly back to Earth in their spacecraft, to retrieve the toy. When Bebop's raygun hits the toy, the meltdown process begins. April O'Neil saves the day by unplugging the batteries.