In "The Last Mabelcorn," Mabel, Candy, Grenda and Wendy travel to the Enchanted Forest to find unicorn hair to help Ford. They find Celestabellebethabelle, who claims she is the last of her kind when Grenda summons the doors to the Realm of the Unicorns. Celestabellebethabelle tells the girls that she will offer a lock of her hair to only the purest of hearts, Mabel steps in and claims she is of pure heart; however, Celestabellebethabelle disagrees, saying she can see through her heart. This prompts Mabel to go on a quest to make herself pure of heart. When Mabel takes on the task of doing a thousand good deeds, the girls return to Celestabellebethabelle only for the unicorn to say she is still not pure of heart, prompting Mabel to cry and try to find the best good she can do. When Candy, Grenda and Wendy get some fairy dust from the gnomes, they use it to knockout Celestabellebethabelle and they attempt to cut a lock of her hair. However before they can do it, Mabel stops them and the unicorn mistakes Mabel as the one cutting her hair. She tells Mabel she will never be pure of heart but two other unicorns hear her. The two other unicorns tell the girls that the pure of heart story is a scam to get humans "get off their backs". This causes Mabel to be engulfed in rage at Celestabellebethabelle for emotionally torturing her. Celestabellebethabelle taunts Mabel, resulting in an all-out feud between the girls and unicorns. Eventually, the unicorns give the girls some treasure just to get rid of them, though only after suffering a beatdown at the hands of the girls.
She is a blue-tinted unicorn, whose horn glows pink or red. Her mane is multicolored with purple, blue, pink, yellow and green. Her eyes are overly large, with only one visible when she is shown in profile, and with long lashes. Her hooves are pink and have blue tufts of hair coming from right above the hoof, and she has three blue sparkles on her rear. Her tail has hair only at the tip, and it is the same style and color as her mane.
- 215. "The Last Mabelcorn"