Cheerilee loses her cheer when life becomes a little too routine. On her birthday, when she learns of inter-dimensional travel, she yearns to soon venture to a new world. Cheerilee and the mane 6 all travel to a Technical High-school in our dimension.

Meanwhile, with the elements no longer in their dimension, Discord has broken free again and seeks to turn the world into a puddle of chaos and insanity. Celestia must quickly scrounge up a counterfeit mane 6 to combat him while she combats her own sister.

Yup.