After Miguel wishes he never had a sister, he wakes up to find it came true. Maya doesn't exist!
It's Christmas, and the Santos family is getting ready for the festivities. Maya, in her enthusiasm, manages to mess up things for Miguel: she spills juice on his book report, volunteers him to hang a pinata in class (a task which makes him take a humiliating fall), volunteers him to wear a too-big Santa suit and follow her around wishing their neighbors happy holidays (his pants fall down in front of everyone), and smudges a painting he was making as a gift to his parents. Frustrated, Miguel angrily declares that he wishes he never had a sister. The next day, he awakens to find his wish has come true; Maya doesn't exist, and nobody's ever heard of her. Paco (who has inexplicably become incredibly articulate) follows him around commenting as Miguel takes in how the world has changed. At first, it seems like all his Maya-made troubles are over... but then Miguel sees how the lack of Maya's influence has adversely affected the world: Maggie and Chrissy aren't friends because they had a difference of opinion (which Maya had previously helped them overcome) Mr. Nguyen isn't their teacher because he felt unappreciated (Maya had made him feel appreciated), Jimmy McCorkle became a bully, etc. Finally realizing how much worse everything is without Maya, Miguel regrets he ever made the wish, and wishes it all to be reversed. Poof! The world goes back to normal. Maya is back, Miguel's painting is still ruined, and Miguel couldn't be happier to have a twin sister.