Rarity convinces Fluttershy to do a porn photo shoot, and all hell ensues. Hilarious hell.

SOURCES

My Little Pony: Friendship is Magic Season 1, Episode 20 - Green Isn't Your Color
1:30 - Ultra Thin Condom Ad from youtube.com/RobertoAlmeida
1:53 & 2:22 Never Scared (Remix) by Bonecrusher.
2:18 - South Park, Season 8, Episode 11 - Quest for Ratings