One day, Celestia and Luna, two scientists living in Ponyville, were exploring a mysterious castle where they found a strange jewel. When they took the jewel back to their laboratory to run tests on it, 15 lights shot out of it. Then three of the lights cause supernatural events and gave three normal girls superpowers.

This is not power ponies, but this is based off Powerpuff Girl Z but you don't need to watch it.