Until the Day it Becomes a Pumpkin! is the Halloween episode of the anime series Ouran High School Host Club.
The episode begins with a full moon and an antique carriage riding through the night while Kaoru's voice is heard saying that at midnight, the carriage will turn back into a pumpkin even though the spell on the carriage isn't cast by a fairy godmother.
Scene skip to the Classroom 1-A with Kaoru daydreaming those very thoughts as Class Representatives, Kazukiyo Soga and Momoka Kurakano, discuss the class event to be held following fall exams and the upcoming holiday. Before anyone can suggest anything, Renge jumps onto a desk and waxes poetic about Halloween, suggesting that the class hold an evening Test of Courage Tournament. Class Rep Soga seems a bit nervous and suggests teams, of which everyone approves. Hikaru and Kaoru come up with the idea that the loser should have their name and picture plastered on the front page of the school newspaper. Soga asks if anyone objects several times while staring directly at Haruhi, who remains oblivious to his not-so-subtle hints, and the motion passes. Back in Music Room #3, the Host Club is cosplaying as vampires; Haruhi and the twins arrive late and still in school uniform. Tamaki is a bit annoyed, but even more so when he learns that they're all going to be absent for a week in preparation for the Class 1-A event. Tamaki's "Theater of the Mind" goes into overdrive as he imagines Haruhi with the twins during said event, clinging to them in the dark from fright. When he declares, "Daddy doesn't like it," the antique carriage reappears with Karou stating in voiceover that "this is the magic spell" (i.e. Tamaki thinking of the Host Club as his family). The 1st-year trio leaves just as Nekozawa emerges from a coffin leaning against the wall of the salon. He tells Tamaki that the Black Magic Club is happy to assist in creating some pure unadulterated terror, then retreats back into the coffin.
Scene skip back to Class 1-A where the Planning Committee discusses arrangements and Soga flags down Haruhi to speak with her in private. He reveals that he suffers with nyctophobia, among other fears, but didn't mention it or nix the event because he didn't want to throw his weight around as class rep. He pleads to be on Haruhi's team because she's so level-headed, but begs her not to tell the twins about his fraidy-cat nature; unfortunately, they arrive just in time to hear about it and the four classmates are soon dubbed, "Team B."
Scene skip to Halloween night with Team B huddled in an Ouran corridor, the twins recounting a horror story about the Evil Clocktower Witch who was once an Ouran student that fell to her death from the clock tower and curses whoever sees her ghost on Halloween night. Class rep is terrified and Haruhi, irked by their teasing, tries to give Soga helpful hints that he deems totally unhelpful. He's about to throw up his hands in defeat until the twins mention Kurakano's name and Soga becomes strangely dreamy-eyed. They all notice and though he tries to deny it, Soga clearly has feelings for the girl. When the twins realize that he's truly a sweet guy (like Tamaki), they wonder with disappointment if they have to help him instead of tease him.
At that moment, Haruhi notices a weird shadow by the window and a skull tumbles down the staircase in front of them, followed by a creepy figure appearing at the top of the stairs who frightens them into running away. Hikaru and Haruhi trigger a trap that lifts them off the floor into a dangling rope net. Kaoru and Soga enter a dark science room only to be greeted by Mori-Frankenstein and Honey-Wolfman, causing them to hare off yet until they're pushed into yet another room by Kuretake and Kadomatsu and locked in. Nekozawa shows his face, delighted with the outcome, while Tamaki frets over the close quarters being shared by Hikaru and Haruhi. As Haruhi cuts them from the net with tiny sewing kit scissors, Hikaru is flustered by her proximity. Kaoru and Soga have a chat and Soga learns that the twins were actually planning to have him appear to be a brave hero in front of Kurakano, moving the class rep greatly. He admits, however, that he's happy with the way things are, just as they are; much like Tamaki and how he views his Host Club "family."
After the two pairs escape, they meet up with the rest of their classmates, who tell them they were worried and called off the contest just to look for them. While Class 1-A stands there, Nekozawa scares them all by casting an enormous shadow of Beelzenef over the dome of the salon they occupy. The next day, the top headline of the school newspaper reads, "Everyone in Class 1-A is a Captain of All Cowards," complete with photographs. Kurakano tells Soga that she heard about his willingness to be scared just so she could be happy and is impressed with him, altering their dynamic from static to evolving. Kaoru notes, "I guess the spell on the carriage can't last forever after all," confusing Hikaru.
The episode concludes with Hikaru and Haruhi walking together chatting, with Kaoru close behind considering what he'll do when his and Hikaru's dynamic changes the day Hikaru finds someone besides him to turn to for comfort and the carriage turns back into a pumpkin. Truth is, he just doesn't know.