Star Comes to Earth

==== In the kingdom of Mewni, on her 14th birthday, Princess Star Butterfly is about to receive the royal magic wand from her parents, the king and queen. She greets the day by sliding down a staircase rail, ruining a family portrait, taming a wild unicorn, and stampeding said unicorn through the throne room. During the ceremony, the queen tells Star that the wand is a big responsibility and must be kept out of the hands of evil forces. Star takes the wand, and it changes to Star's own personal design, and Star assures her mother that she can handle it. Unfortunately, she manages to set the kingdom on fire with it in under a day.

The king and queen decide to send Star away. Star is afraid that they're sending her to St. Olga's Reform School for Wayward Princesses, but instead, her parents are sending her to Earth, where she can learn to use her powers in safety. Royal servant Manfred uses a pair of dimensional scissors to cut open a portal to Earth. Star says goodbye to Mewni as Ludo's minion Buff Frog watches and laughs.

At Echo Creek Academy on Earth, King and Queen Butterfly convince Principal Skeeves to enroll Star (with a bribe of a chest full of gold and jewels). They advise the principal to provide the curious and naïve Star with a guide, so the principal appoints "safe kid" Marco Diaz. As the disgruntled Marco shows Star around the school, he mentions that he would like a little danger in his life. Star obliges by using her wand to turn a butterfly into a screeching winged monster. After Star tells him who she is, Marco, frightened by Star's powers, declares the tour over and races home.

When he reaches his house, Marco finds Star talking with his mom and dad. They tell Marco that Star will be staying with them during her time on Earth. Star immediately wins Mr. and Mrs. Diaz over with her upbeat personality, and when Marco mentions puppies also have it, she gets the idea to use her wand to create a litter of puppies, though they end up being laser-shooting puppies. As Marco shows Star to her room, Buff Frog watches from outside. He uses dimensional scissors to travel to a dark castle and reports to the villainous Ludo about Star's location.

Back on Earth, Star uses her magic to expand her room into a large castle loft. When Marco wishes he had a similar room, Star tries to make one for him but accidentally creates a black hole that sucks in everything from his room. Noticing Marco's frustration, she tries to cheer him up by making a small sun over his head, but it turns into a rain cloud. Fed up, Marco decides that if Star's moving in, he's moving out. Climbing out the window and falling into a bed of cacti, Marco walks off in anger.

That night, outside the Stop & Slurp, Marco tries to get drink refills from passersby due to his rain cloud getting him banned from entering. Star appears to get rid of his rain cloud and apologize for inconveniencing him, saying that she'll find another family to live with. Suddenly, Marco notices the arrival of Ludo and his minions. Ludo commands his minions to attack Star, but Marco protects her with a show of karate. Star and Marco team up to defeat Ludo's minions. Ludo admits defeat and gathers his beaten minions through a dimensional portal, vowing revenge on Star before disappearing.

Marco is impressed with his and Star's teamwork, to which Star admits that he's right. Becoming serious again, Star goes to pack her belongings. However, Marco quickly stops her and says he wants her to stay with his family, and Star thanks him with a hug. As the two return home, Marco is excited about fighting more forces of evil, and Star pokes fun at his "wild man" personality.