During the opening Sequence, the scenes displayed on the Blimp are scenes from the Manga that didn't make it into the Anime Adaptation, including Kaguya & Shirogane's trip to the Movie Theater & the Cosplay chapter featuring Cat-Maid Kaguya.
Due to Production Restraints, the Overtly Christmas Themed Film winded up releasing in February in America.
During the Kaguya-Chan scene, when Shirogane is comparing Kaguya's current Brain state to an Orange, the Shooting Stars flying past are the Birdson of Birdville, the Movie that Chika suggest the 2 see in the First Episode, and Shirogane's Papier-mâché Dragon that he made & stole for the Sports Festival in season 3.
The film primarily adapts Vol. 14 & 15 of the Manga.
Some Fans were frustrated when the Film only received a 2-Day only Special Release in America after previous Anime Films, such as Dragon Ball Super: Super Hero, One Peice: Red & the Quintessential Quintuplets Movie, Received more Traditional Theatrical screenings in more Theaters.