User blog comment:PlantyThePottedPlant/Random Topic Blogging II: Electric Blogaloo/@comment-1659929-20120129042145/@comment-4353345-20120129062650

@Lala: The zebra appeared after she thought she was hallucinating, like a Placebo effect. So, considering the zebra's first appearance was "all in her head", she simply had the zebra in her mind her entire life an had not come out until he had a good reason. And once he was out, he wouldn't go back in.

See? That makes perfect sense.