The TV movie follows Star as she returns to her home dimension of Mewni where she discovers that magic is disappearing throughout the kingdom. Star must dig deep and challenge archnemesis Ludo in an effort to save her family and kingdom.
Return to Mewni
A couple of days after "Starcrushed", Marco's parents try to console Marco who will not stop thinking about Star who, unbeknownst to him, is watching him with the seeing eye. Meanwhile on Mewni, Star and Moon Butterfly take the Magical High Commission members to the sanctuary to get revived, but their carriage breaks down because of the fritz. As they try to set up camp for the night, some of Ludo's rats appear. Star, who still fails to understand that her wand is tainted, tries to attack them, but her and Moon getting distracted causes them to lose track of the Commission who float away after the rats let them go. They get them out of a thorn tree before making it to the sanctuary. When they try to revive the members, they learn that the well spring has been corrupted with dark magic. As they try to think of "Plan B", Star accuses Moon of being afraid to fight back, but she tells her that she used to be carefree like her until Toffee killed her mother Comet, something Star was unaware of. Moon explains further how in order to defeat Toffee the first time, she had to make a deal with Eclipsa who she reveals is "very much alive".
Moon the Undaunted
In flashback, a teenage Moon has recently lost her mother and is pressured by her generals and the Commission to do something; either go to war or sign a peace treaty. The only person who shows her any compassion is River while Glossaryck is still sad to the point that he offers no help. She spots the forbidden page in the Book of Spells and decides to seek out the writer: her ancestor Queen Eclipsa who has been crystallized for an undefined crime. After partially unfreezing her, she agrees to teach her the spell on the condition that she be freed telling her that a queen's promise is more powerful than anything else. Upon teaching her the spell, Rhombulus refreezes her. Moon heads out to the monster camp to speak directly to the general Toffee. She threatens them and proceeds to fire off a spell that darkens her arms and blasts Toffee's finger off. When he realizes that his finger cannot grow back, the rest of the monsters flee in terror and Toffee calmly walks away. The generals and Commission are shocked at Moon's resolve, but she tells them that she is their queen and she will do what is necessary.
Book Be Gone
Ludo awakens to find that his wand is now embedded into his hand. He finds Glossaryck, attempting to make a solid fudge ball, and asks what happened. He tells him that he defeated the Commission which makes him happy and he tries to write his accomplishment into the Book. However, the Book will not let him, as Glossaryck states that he is no longer the owner. Ludo tries in vain to have the Book remain open for him and even uses a spell that ends up blasting him miles away. After being tended to by mer-people, Ludo treks back to the temple in an effort to get Glossaryck to tell him more about not being the owner. He continues to be vague and after talking directly to the book with no response, he angrily tosses it into the fire. Toffee takes over and tells Glossaryck that while he wanted the book destroyed, Ludo did it for him. Glossaryck fades away and Ludo comes to; regretting his actions. Toffee, through his hand, convinces him that they must attack Butterfly Castle.
Marco and the King
King River tries to take care of the kingdom by partying it up every day, but he and his subjects wear down quickly. While trying to restart another party, Marco arrives to see Star, but is taken aback at how unkempt the castle is. River tries to explain how because Moon and Star are gone, he has been left in charge. Marco points out how the kingdom is in disrepair and that all the citizens look unhappy. While trying to calm everyone down, River accidentally alerts a giant monster that begins terrorizing the town. River gives up in defeat; admitting that he needs common things like his clothes picked by Moon, who had left an entire room of prepared sets for him. Marco tells him that he needs to stand firm as he is in charge. With newfound confidence, River gives a pep talk to the Mewmans and has them use their traits to defeat the monster. However, the monster simply misinterpreted River's direction and promptly turns around and leaves. As everyone celebrates, they are caught off guard by Ludo arriving with his army.
While resting in the sanctuary, Star and Moon get a rude awakening when everything gets sludged over. They escape with Star once again, criticizing Moon for avoiding facing Toffee. Star takes Moon to hide out at Buff Frog's house. Moon is taken aback by Star being friends with a monster, but with no other options, they stay. Buff Frog is updated on what is going on and tells them that Ludo/Toffee has taken over Butterfly Castle. When Moon refuses to go and help, Star tells Buff Frog to distract her while she sneaks out. They end up playing Puddle Defender, a board game that seems to be heavily biased against Mewmans. While Star tries to sneak out, Moon and Buff Frog get into an argument where Moon accuses him of acting savage, hence her perception, while Buff Frog accuses her of not being well informed. When she accuses him of not understanding parenting, Buff Frog angrily rebuffs her, as he has children of his own and refuses to help Star escape; exposing her. As Star is sent to the bedroom, Moon apologizes to Buff Frog. However, Star learns that Katrina, the youngest tadpole, can talk and reveals a secret exit (which the tadpoles use to go clubbing). Star reveals that she has no plan to defeat Toffee and will just run in headfirst, much to the tadpoles' annoyance.
Ludo has taken over the kingdom, but discovers that he is not popular at all, despite having merchandise. River and Marco have been imprisoned and he demands that River make him popular or else he will levitate him into the sky. He drops a stick of butter, which he was using to get a key around his neck, and Marco successfully slips out of his cuffs. However, River incompetently eats the butter, forcing Marco to go and find the key. He makes his way to Ludo's bedroom and discovers that Ruberiot, the minstrel, Foolduke the jester and Mime Girl have been hiding in the vents and living off of Ludo's leftovers. Ludo returns and Marco, in a Ludo mask, and the entertainers put on a impromptu show to distract him. However, the entertainers get into an argument and are kicked out. Luckily, they snagged the key and go to free River. However, River chooses to stay so that he can be close with his people. Ludo returns and takes River to levitate him into the sky. After doing so, Marco prepares the entertainers for war.
As Ludo continues to abuse his power in Mewni, Star sneaks into the castle to attack him and witnesses first hand his corrupted state. Star tells Ludo that Toffee is controlling him, but Spider is able to capture her in the meantime. After getting imprisoned, Marco arrives to rescue her along with the entertainers (Le Resistance), but while plotting are stopped by Ludo who takes Star and imprisons the others. Ludo admits that he is finally aware of Toffee's influence over him and asks for help. Moon and Buff Frog break Marco out (leaving the entertainers behind) and search for Star. Star uses the whispering spell to free the magic in Ludo's hand and there is a big blast. Marco, Moon and Buff Frog find Ludo's body with Star's voice coming through him. She has ended up in another realm full of black liquid and as she loses contact with the others, comes face to face with a giant black liquid version of Toffee.
Toffee tells Star that they are in what is left of her magic and takes control of Ludo again. Moon agrees to return Toffee's finger in exchange for Star's freedom. Toffee resurrects (spitting Ludo out), but leaves Star in the darkened magic; casually leaving everyone in sad defeat. Star desperately searches for what is left of her own magic, but faints from exhaustion. She finds herself with Glossaryck in an unknown realm. As he cooks a pot of soup, Star angrily confronts him on recent events and realizes that he is trying to teach her another lesson. She dips into the soup and escapes the realm with a new wand and a upgraded butterfly form. She blasts Toffee into a gooey mess and is reunited with Moon, Marco and Buff Frog. As Toffee uses the last ounce of his strength to threaten them, Ludo drops a pillar on him; killing him for good. Ludo asks Star to send him back to the void so he can find himself some more. While King River returns on some eagles, Moon checks on Eclipsa who is still encased in crystal, however as Moon leaves, the crystal cracks.
- Eden Sher as Star Butterfly
- Adam McArthur as Marco Diaz
- Michael C. Hall as Toffee
- Alan Tudyk as Ludo/River Butterfly
- Sonny Ashbourne Serkis as Young River
- Artt Butler as Mr. Diaz
- Nia Vardalos as Mrs. Diaz
- Grey DeLisle as Moon Butterfly
- Katie Driver as Young Moon
- Amy Sedaris as Mina Loveberry
- Zosia Mamet as Hekapoo
- Kevin Michael Richardson as Rhombulus
- Fred Tatasciore as Buff Frog
- Esmé Bianco as Eclipsa Butterfly
- Natalie Palamides as Foolduke
- Patrick Stump as Ruberiot
- Jeffrey Tambor as Glossaryck
- "King Ludo is Great"
- This is the first animated movie to premiere on Disney XD (unless one counts the movie version of the Gravity Falls series finale, "Weirdmageddon").
- The Diazes end of school year party decorations seen in "Return to Mewni" didn't appear in "Starcrushed", so this is likely a continuity error.
- The missing part of Star's wand is re-merged in "Toffee" and takes on a third new appearance.
- Eclipsa Butterfly speaks for the first time in the series.
- One of the Laser Puppies is revealed to be named Barko Diaz.
- This episode premieres the new intro as well as the new ending credits.
- While not the first time Star does not appear, "Moon the Undaunted" is the first time she is not even mentioned for the whole episode.
- "In Return to Mewni", Star and Moon's carriage briefly turns into a wagon that reads Butter/Flyer, a reference to the actual wagon brand Radio/Flyer.
- In "Puddle Defender", Buff Frog's tadpoles are noticeably getting older.
- Some of Buff Frog's board games are parodies of real-life board games: Hungry Hungry Mewmans (Hungry Hungry Hippos), Monstropoly (Monopoly), and Mewman Trap (Mouse Trap). Additionally, Castle Crushers sounds similar to Castle Crashers which is not a board game, but a video game.
- In "King Ludo", there is a toilet in King and Queen Butterfly's royal bathroom, even though River is unfamiliar with flush toilets in "Royal Pain". However, it's possible that toilets were installed in the castle between that episode and this one.
- The Battle for Mewni at the Star vs. the Forces of Evil Wiki
- Return to Mewni at the Star vs. the Forces of Evil Wiki
- Moon the Undaunted at the Star vs. the Forces of Evil Wiki
- Book Be Gone at the Star vs. the Forces of Evil Wiki
- Marco and the King at the Star vs. the Forces of Evil Wiki
- Puddle Defender at the Star vs. the Forces of Evil Wiki
- King Ludo at the Star vs. the Forces of Evil Wiki
- Toffee at the Star vs. the Forces of Evil Wiki