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.
LazyTown has a new superhero and her name is SportaStephanie! In this special one-hour episode, Sportacus takes a vacation and leaves LazyTown in the hands of his good friend Stephanie. As SportaStephanie, she faces her first big challenge when Robbie unleashes a hero-hating machine called Robo-Dog.
Mayor Meanswell is once again getting ready to present the Person of the Year trophy to Sportacus, but can't seem to keep it a secret that Sportacus is the winner. When he hears that Sportacus is winning again, Robbie decides to put a stop to it. Considering the past failures of his evil plans, he decides to hit Sportacus with several of his past failures, hoping that they'll combine into a success.
Stingy is tired of the mess in LazyTown. He tries to get them to clean up all of the garbage. But the kids aren't interested, and their mess continues to grow. Robbie Rotten overhears this and realizes that if he makes a huge mess in LazyTown, the kids won't be able to play any more. He then creates a trash shooter that loads up the town with garbage. But Robbie's plan ends up backfiring when his trash shooter gets stuck and buries LazyTown.
The Mayor warns the kids to stay away from an old, unsafe castle but Trixie ignores the warning and convinces the kids to join her inside. Meanwhile, Robbie poses as a ghost to scare the kids into not playing any more. The kids get trapped in the falling castle and Sportacus arrives to save the day. Trixie admits what she did and the kids learn a valuable lesson in following the rules.
When Robbie Rotten realizes that Sportacus started learning all of his hero skills when he was a boy, Robbie turns Sportacus into a 10-year-old. When Stephanie discovers who the boy really is, she and the kids join Little Sportacus on a mission to Robbie’s lair, so he can be changed back to his larger self.
It's the Christmas season in LazyTown and everyone's getting ready for a holiday party. Robbie Rotten soon spots this, but declares that he wouldn't go even if he was invited. He hatches a plan to dress up as Santa Claus and spoil everyone's holiday fun. Meanwhile, Stingy is having trouble understanding the spirit of Christmas. He just loves the gift-getting, but can't quite seem to get into the gift-giving