Arthur is looking forward to having his friend the Brain spend an entire weekend at his house, but then the Brain shows up and starts acting a little too much like the perfect family member.
When Arthur and his friends buddy up to train for a race that will raise money for their school's literacy drive, Fern seems uninterested in winning or even improving her speed.
When Buster impulsively drops a Cybertoy into Arthur's backpack in the drugstore one day, he feels so guilty that he finally confesses to his friend and they try to return the popular toy before anyone else finds out.
Arthur and his friends set out to make the world's largest pizza so that their feat can be recorded in "The Book of Incredible and Amazing World Records."
Arthur's Grandma Thora, a marbles champion, trains him for the first-ever Elwood City Marbles Tournament, but does not tell him that she will compete against him.
Mavis tries to pursue her goal of playing fairy godmother and granting wishes to those around her, but she finds the process trickier than she thought.
Frustrated by Santa's slowness at Christmastime, Muckle the elf creates a mechanical replacement called the Deliverator and proposes a series of contests to prove that it can do Santa's job better than he can.
When Arthur fails to show up for his second piano lesson, his music teacher dismisses him. Now Arthur has to decide how much he wants to learn to play the piano.