It's a peaceful summer afternoon. The kind of summer afternoon that just causes foals to want to get into trouble. The Cutie Mark Crusaders have answered that call (as they so often do). Their latest Crusade takes them deep into the Everfree Forest, where they find the ruins of Human civilization. Eager to start their next adventure, the Crusaders recruit Rainbow Dash, and Lyra (Ponyville's resident crackpot anthropologist), and they set out to explore. However, instead of the hoped for divine tomb, they've really just broken into a hastily sealed nuclear waste repository. The Crusaders get bored, and everypony gets soaked in radioactive sludge.
Edited by Sourichan