To protect the Mystery Shack from Bill, Ford reveals they need unicorn hair to create a magical barrier [3]. Mabel, being the resident optimist, leads Candy, Grenda, and Wendy to find the Celestabellebethabelle the unicorn [4]. However, the unicorn reveals herself to be a judgmental snob, claiming Mabel isn't "pure of heart" enough to deserve the hair [5]. After various failed attempts to become "perfect," Mabel eventually realizes the unicorn is a fraud who uses the "pure of heart" line just to get humans to leave her alone [6]. The girls end up taking the hair by force in a hilarious "magical" brawl [6].
The flashback scenes are some of the most visually striking in the series, cementing Bill Cipher as a truly terrifying antagonist [9]. [S2E15] The Last Mabelcorn
The episode subverts the "magical girl" trope. Mabel learns that trying to be "perfect" is a lost cause and that being a good person doesn't mean being a saint—it means standing up for yourself and your friends [6]. To protect the Mystery Shack from Bill, Ford