After watching Fluttershy tail-slap poor Twilight today, I've had this phrase running through my head!
I must exorcise it with drawin'!
EDIT- After several complaints about Flutterjerk's strange leg positioning, I've made some slight changes.
I tried to recreate her unusual hoof placement from the episode. In this scene she was sort of pivoting her body and planting her back left leg at the same time. It created some foreshortening of her torso and her sides partially covered the back leg. I thought it looked pretty interesting, as it's an angle we don't see drawn very often.
Alas, quite a few people seem to think I decided to add a few pounds to poor Fluttershy or just derp up her limbs for the heck of it. I went ahead and changed things to reflect a little more "normal" looking position. Hope this clears up some of the confusion!