My Little Pony: Friendship is Magic S1 Ep12 "Call of the Cutie"

Apple Bloom becomes worried when two stuck-up classmates, Diamond Tiara and Silver Spoon, get their cutie marks and taunt Apple Bloom as a "blank flank" for lacking hers. Apple Bloom starts striving to find her own talent and get her own mark, asking advice from her sister Applejack and her friends. Despite her efforts, she remains without her cutie mark. She finds herself caught within the Cute-ceañera celebration for Diamond Tiara and Silver Spoon, and tries to leave before she is ridiculed. Just as she is discovered and teased by her classmates, two other fillies who lack cutie marks, Scootaloo and Sweetie Belle, stand up for Apple Bloom, assuring that she still has lots of potential in her life; the rest of the partygoers soon take more interest in Apple Bloom and her new friends than Diamond Tiara and Silver Spoon. After the party, Apple Bloom, Sweetie Belle, and Scootaloo form the "Cutie Mark Crusaders" to earn their cutie marks together.