Main characters aside, every season features episodes focused on the exploits of recurring characters. This includes a trio of younger ponies (Apple Bloom, Scootaloo and Sweetie Belle) who call themselves the "Cutie Mark Crusaders" and share adventures trying to discover their talents in life and receive their "cutie marks" until the season five episode "Crusaders of the Lost Mark", where they finally receive their cutie marks. The alicorn princesses (Celestia, Luna and Cadance) frequently aid the Mane Six in their service to the inhabitants of Equestria. Beginning in season four, the reformed villain Discord becomes a reluctant ally of the Mane Six. Beginning in season six, the reformed villain Starlight Glimmer becomes Twilight's protégée. Beginning in season eight, the leaders of Equestria's allied nations send five of their heirs to Equestria to receive an education from Twilight. An extensive cast of over 200 minor and guest characters, designated as "background ponies", are used to fill out crowd scenes and serve as visual gags in episodes.