At Ludo's monster temple, Star sets up for a party to bring Mewmans and monsters together with the help of Marco, Rich Pigeon, and Pony Head. But the party guests stand completely isolated from each other, with Mewmans and royals on one side and monsters on the other. Once Rock Johansen takes initiative and compliments one of the monsters on his jeans, the rest of the Mewmans and monsters start to interact. Meanwhile, Miss Heinous, Gemini, and Rasticore sit in their car outside, waiting to make a move against "Princess Marco".
Tom approaches Star and asks for a dance, but Star says she's too busy making everything at the party perfect. Tom laments that Star has been working so hard lately she hardly has any time for him, but Star promises to make it up to him later. He confides in Marco, but Marco says uniting Mewmans and monsters is really important to Star. Meanwhile, Slime Monster befriends Princess Spiderbite, and they accidentally stumble into a secret temple chamber with monster statues, where they are attacked by something huge.
As the party guests make a toast to Star, Princess Spiderbite returns covered in slime, claiming to have been attacked by a monster. The Mewmans think she was attacked by Slime Monster, but the monsters believe Spiderbite did something to him because she returned without him. The party guests start to notice that other monsters have also gone missing, and tension starts to build between the two sides. Star assures everyone that she'll get to the bottom of this and leaves Pony Head to keep them entertained with jokes. Tom tries once again to get a dance with Star, but she blows him off in favor of finding the missing monsters.
Deeper inside the temple, Star and Marco find a small campsite where someone has been staying. They quickly discover it to be Mina Loveberry, who has been capturing monsters all evening. Star tells Mina to let them go, but Mina refuses, determined to protect the temple and firmly entrenched in the belief that all monsters are evil. As Star tries to reason with Mina, Miss Heinous crashes down through the ceiling, and Star and Marco are captured by Gemini and Rasticore.
Marco is hooked up to Miss Heinous' youth-draining machine, and Miss Heinous prepares to drain his energy. However, when her cheek emblems start glowing, it activates an ancient magic in the temple and opens a nearby room. Inside, Miss Heinous finds dolls, toys, and a baby crib—things she remembers from her childhood. Mina rises from the rubble and reveals that Miss Heinous is actually Meteora Butterfly, the half-breed daughter of Queen Eclipsa and her monster husband.
Mina prepares to destroy Miss Heinous for being the offspring of a monster, but Star stops her, needing more answers. When Mina refuses to stand down, Star attacks her with the wand, causing a battle to break out. While Star holds Mina off, Marco frees the captured monsters, and Miss Heinous, Gemini, and Rasticore make their escape. Tom soon appears looking for Star, and he joins her and Marco in the fight against Mina Loveberry, but she quickly overpowers them. When Mina notices Miss Heinous is gone, she crashes the party upstairs looking for her. Before Mina can harm the party guests, Star restrains her, and Mina tells Star that she helped the most dangerous monster in Mewni escape.
All of a sudden, Rhombulus and the Butterfly Castle guards storm into the temple, and Mina makes her getaway. The party—which Star had apparently thrown in secret—is cancelled, and the monster temple is sealed off. Rhombulus scolds Star for throwing a party in such an important place, but he refuses to explain why it's important. Tom appears and apologizes to Star for being so needy during the party, but Star says it doesn't matter. She laments that her efforts to unite Mewmans and monsters have been ruined, and she is now feeling more lost than ever after discovering the truth about Miss Heinous.
The castle guards arrest the monsters, but Star demands they be let go, not wanting Mewmans to be given special treatment. Star apologizes to the monsters for everything that happened, but the monsters say it's okay, being used to such harsh treatment. Meanwhile, Miss Heinous, Gemini, and Rasticore sneak away through the nearby woods. When Gemini addresses Miss Heinous by name, she says that's not her name. As she stands under the moonlight with yellow eyes, pointy ears, fangs, glowing cheek emblems, and a left arm covered in scales, Miss Heinous declares, "My name is Meteora."
- Pony Head
- Tom Lucitor
- Johnny Blowhole
- Prince Richard Pigeon
- Prince Larry Kelpbottom
- Prince Rock Johansen
- Princess Jaggs Jaggy
- Princess Penelope Spiderbite
- Headphone Jones
- Spider With a Top Hat
- Lady Whosits
- Eclipsa Butterfly (mentioned/depicted)
- Globgor (depicted)
Title in other languages
|Hebrew||מכת מפלצות||Monster Strike|
|European Portuguese||Festa Monstruosa||Monstrous Party|
View the episode transcript here.
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- This episode marks the third season's mid-season finale.
- Actress Juliana Hansen guest-stars as Princess Spiderbite.
- Daron Nefcy's husband Bobby Miller plays Slime Monster.
- The episode is animated by Rough Draft Korea, but is somehow mistakenly credited as Sugarcube.
Revelations and continuity
- Star continues her efforts to unite Mewmans and monsters after "Starfari" and "Death Peck".
- Considering the Mewman side of the party were not all the same race as Star, it can be inferred that "Mewman" does not simply refer to the humanoid race, but also with any race that is in one of the allied kingdoms.
- Star wears the same outfit and hairstyle she wore to her Song Day in "Face the Music" while Marco wears the same outfit he wore during the school dance in "Bon Bon the Birthday Clown" and Pony Head wears the same outfit she wore during the Silver Bell Ball in "Club Snubbed".
- The people at the party do the same "sword hand dance" that Eclipsa imitated from Marco in "Sweet Dreams".
- Rasticore's body has almost fully regenerated.
- Mina Loveberry returns after her absence since "Starstruck".
- The reason for her cameo in "Book Be Gone" is revealed to be because she was protecting the temple from monster invaders.
- Miss Heinous is revealed to be Meteora Butterfly, the Mewman/monster hybrid daughter of Queen Eclipsa and her monster husband Globgor.
- The Monster Temple is revealed to be the original home of Meteora and her parents.
- Star finally uses the Spider With a Top Hat spell in practical combat against Mina.
- The episode's title is similar to, and a reference to, the 1962 novelty song "Monster Mash".
- One of the books at Mina's campsite is called Secret Tuxedo, a reference to Tuxedo Mask from the anime series Sailor Moon.
- Another book is called Thirty Shades of Magic, a reference to the novel Fifty Shades of Gray that later got adapted into a film trilogy.
- When Miss Heinous, Gemini, and Rasticore spy on Marco from Miss Heinous' car, the tracking device first appears in Gemini's hand. In the very next shot, the tracking device is in Rasticore's hand.