One night, Jake is attacked by an army of sewer trolls. He tries to call Fu for help, but Fu is playing a card game with Esmerelda, a Goblin, Shark Lady, and an Abominable Snowman.
At the DMC, Fu's animal guardian license goes down (means it was expired again) and Jake gets a new magical guardian, a talking monkey named Bananas B. Meanwhile, the necklace that Jake got from the trolls shows that the necklace belonged to Chang.
Chang escapes from prison. The next day, Jake goes to school and forgets about Fu's test. Fu has to do the test with an old Gnome named Mister Krunkers. For the first test, Fu and Krunkers both have to defeat 4 hobgoblins, but Krunkers is very dumb so he hits Fu with a huge wooden club. Next, Fu tells Krunkers to had a pitch of Leprechaun Dust in the orange potion, but Krunkers once again makes a bad mistake on purpose, so he adds the wrong ingredient in the potion and it turns blue, resulting in a huge explosion. Thus, Fu fails the test.
When Jake, Spud, and Bananas arrive back at the shop, Chang suddenly appears out of nowhere and says, "Lao Shi's grandson, we meet again." The sewer trolls attack the heroes and it is revealed that the trolls were working for Chang. Chang is about to kill Spud by crushing his head, until Trixie stops her. Chang blasts sphinx hair nets and traps Jake. Bananas B joins with Chang, and the two villains escaped after they captured Jake.
Fu is walking sadly and wants to be back with Jake. At a carnival, Jake releases himself and kills all of the trolls, but Chang is about to kill Jake, until a blue beaker hits her. It freezes Chang and she falls. It is revealed to be Fu Dog, who then rescues Jake. Chang and Bananas escape, but she says she will come back for Jake and his grandfather.
At the DMC, Jake tells the creatures that Fu is a loyal friend, and his license is returned to him. The episode ends with Jake and his pals playing a card game.
During the end credits, Fu talks about other animals besides Shark Lady. There were other magical animals such as Legal Eagle, Lounge Lizard, and a Duck with Goose Pimples, which had a habit of popping pimples and frightened Fu.
- The title is a pun on "Nobody's fool".
- Fu breaks the fourth wall at the end.