Pony Shrugs are a very popular reaction image used by pretty much all parts of the MLP fandom, Ponichan or otherwise. The pose was based on an earlier meme called "I Dunno LOL" which were image macros depicting anything from animals to inanimate objects shrugging, hooves lifted outwards and the pony standing but not revealing the lower body. The original Pinkie Pie pony shrug was drawn by MegaSweet and posted on /co/ as a template on December 12, 2010 , then uploaded to his DeviantArt account in January. It almost immediately exploded in popularity. Pony Shrugs for the rest of the mane six characters were made and colored in ten seconds flat, and soon a plethora of pony shrugs for background characters (and even OC ponies) were made as well.
Having a pony shrug can be seen as a rite of passage for a character into "popularity" among the fandom. A good measure of the character's popularity can be taken by how much time it takes for a shrugpony of that character to be made after the character has been introduced on the show.
On the ponychan's theme setting, there is a pinkie pie option. Choosing this option lines the edges of the window with the original pinkie pony shrug.
Going onto the /troll/ board of ponychan results in your theme being changed to "pinkie pie" by default probably to tie in with the heading "WHY ARE YOU EVEN HERE"
Feel free to add whatever shrugpony images you may have! An OC is fine too, but please put official characters before OCs when adding images.