It's Friendship is Witchcraft. Jenny does the Mane 6 and Spike and Luna, Griffon does DT and Silver Spoon and Celestia. Then they get random friends for other voices usually.
http://www.youtube.com/watch?v=1QfsI77p60Q
neat remix.
Zeus got distracted by a straw, and therefore Loki wins by default the Epic Battle of the Gods!