Somnambula is a witch whose powers are stronger when she is younger. She has a canary named Kyrie whom she holds prisoner. She makes Kyrie sing to attract the ponies in a trance. She is voiced by Jane Curtin. As soon as Somnambula was younger, she creates a magical circus and leads the ponies to it. She takes away the youth of the earth and pegasus ponies to make her younger and the youth of the unicorn ponies to make her powers stronger and stores them in a crystal.
She also created illusions of the Big Brother Ponies' fantasies to keep them distracted. Kyrie aids the Baby Ponies and Spike in rescuing the other ponies. Seeing Buttons in agony, Slugger destroys the crystal causing Somnambula to rapidly age back to an old woman. The circus disappears and the ponies regain their youth.