Spring Tide’s size shifting is involuntary and uncontrollable, but Canterlot science has found a way of temporarily cutting her ties with the moon’s power, which has the effect of keeping her one size until the potion wears off. Usually the potion lasts for a good long time, but under certain circumstances, Spring is able to overcome the potion’s effects and resume her normal ebb and flow. When this happens, it’s best to get another potion in her before she gets TOO big, since the potion will lock her in at that size until it wears off.

Sometimes, if she’s feeling rambunctious enough, she’ll run off. If it takes her handler too long to find her, she’ll overshoot a “safe” size and be forced to ride out the normal cycle until she’s a good size to stay at. These situations happen WAY too often for her handler to approve of.

Link to tumblr for full-size: http://goattrain.tumblr.com/post/14.....nvoluntary-and