Plot
In each book, Ricky Ricotta, a mouse, with the help of his mighty robot, saves the world from an evil villain. Also, the books each have an alien creature from a different planet in order from closest-to-sun to farthest-from-sun including Earth, as the villain of the first book is from Earth. The reader could see the villains being jailed in each series and later notice the familiar villains from previous books.