A little boy was nicknamed Sloppy King. He doesn't care about hygiene, throws waste away, and eats dirty things. The Secret Agent of the Mouse Kingdom, the Pointy Mouse, took a fancy to him and dropped a pill in the orange water. After the Sloppy King drank it, he suddenly became a villain the size of a mouse. He followed the pipe rat to the mouse kingdom. He didn't want to stay there, and ran away several times, but the mouse kingdom was full of soldiers, and finally he was locked up. It turns out that the Rat King wants to dominate the earth and conquer mankind. The little sloppy is their experiment in researching and destroying the "secret bacteria" of human beings. Xiao Jian is determined to escape the prison and report the "secret germs" to the people on the ground. With the help of the kind-hearted mouse, he finally found the secret map after many trials and tribulations. Unexpectedly, he was caught by the ambush under the mouse king again, and the poor white mouse was also pushed down the deep valley. Dr. Shuguo was happily experimenting on Sloppy King. Because the faithful kittens and puppies secretly put medicine into their pockets, Dr. Shuguo ended in failure. The Rat King roared to kill Xiao Slutty, and it happened that the Princess of Rat Country was about to get married. The father-in-law uses the talents of the sloppy king to manage marriages like a human being for himself. Xiao Yun cleverly used firecrackers instead of fireworks, blasting the mouse kingdom down. He returned to the ground with the cats and puppies who were in distress. The sloppy king tasted the bitter fruit of sloppy, and he has never been sloppy again.