When Stephanie arrives in LazyTown, to spend the summer with her Uncle Milford, she finds that she has trouble making friends because all the local kids spend all their time indoors playing video games. So, her uncle enlists the help of Sportacus, an athletic hero who encourages the kids to have fun by remaining active. Unfortunately, this doesn't sit well with Robbie Rotten, a lazy cheat, who takes pride in having LazyTown be the laziest town around, so he plots to get rid of Sportacus.

The kids must face Robbie Rotten in a sports competition without the help of Sportacus after the villain causes the athletic hero to suffer a Sugar Meltdown brought on by a candy apple.

The kids are compelled to do whatever Robbie says and not question him when he disguises himself as Sportacus and gets them to act lazy.

Ziggy tosses out a toothbrush, a birthday gift from Sportacus, in favor of a taffy machine from Robbie Rotten. Soon, Ziggy is unable to stop the gadget when it begins to get out of control and covers LazyTown in taffy.

Sportacus loses his Crystal and offers a reward of one free wish to whoever finds it and returns it. Robbie sees this as the opportunity to get the free wish and use it to wish Sportacus out of LazyTown.

Sportacus tries on a new pair of shoes, unaware that they are actually radio-controlled boots that Robbie will use to ruin Sportacus' athletic skills during Spectacular Sports Day.

Ziggy tries to be a hero just like Sportacus, but his antics start getting him in trouble when he messes up the construction of the kids' new clubhouse.

A missing page from Stephanie's diary causes trouble amongst the kids.

The kids enter a treehouse building contest, but find it difficult working with Stingy because he doesn't know how to work as a team.