You'll only end up with a pony in your pony

My great-grandfather used to tell me, "Don't chase after Ponies because you'll only end up with a Pony in your Pony." I never quite understood his advice until one Hearth's Warming Eve, I was gardening with my best friend Fluttershy. All of a sudden, we found an underground tunnel! It was Ponyish and spooky sounds came from deep within. Fluttershy saw something interesting inside, jumped in, and I never saw her again. Great-granddaddy was right!