Megan Williams is an industrious, sweet-tempered, and very beautiful 12-year-old girl. As designated bearer of the Rainbow of Light, she regularly assists the residents of Ponyland. She is a natural leader - gentle and motherly, resourceful and mature, patient and kind and thoughtful (far more so than most people her age). In times of crisis, the Little Ponies often fly across the rainbow to find her.
Megan lives with her brother and sister on a ranch, where they keep a horse named TJ and a bull named Tauro. (The siblings' parents are never seen or mentioned.)
She was first brought to Dream Valley by Firefly, in order to help save her fellow ponies by defeating Tirek. During her quest, Megan encountered the Sea Ponies and the Moochick; the latter gave her a heart-shaped locket which contained the Rainbow of Light. After Tirek's defeat, Firefly brought Megan back home, the girl kept the locket.
She also makes a brief appearance in the 2018 Equestria Girls "Rollercoaster of Friendship" special.