I don't know if I'm taking this to heart seeing as how we've seen outhouses before. In The Last Round up when Pinkie needed to pee and met Applejack in Dodge Junction.
Update! Courtesy of GoldenSandslash.
For those of you who don't want to imagine Pinkie Pie Scat Porn, Lauren Faust did later tweet saying that she didn't think this all the way through. This is basically non-canon. I mean, think about it. They EAT flowers, Rose gave Pinkie a flower for her hair, and Dashie even tried to eat cider off the ground. Thank god this isn't really the case.
Of course, if you are a scat fetishist, then feel free to imagine that stuff that I just talked about.
These update tweets are:
Too lazy to take screencaps. :P