A high maintenance person at the Burning Man Festival who is unprepared for the harsh camping environment and becomes a burden to their camp-mates.
Burner #1: "Can you believe that Sparkle Pony over there brought 60 costumes but only 2 gallons of water and some ramen noodles?"Burner#2: "Yeah. They asked me where the food court was located."
We all have Sparkle Ponies in our lives - and are sometimes Sparkle Ponies ourselves. Sparkle Ponies look pretty or make us feel better or happy, but are often useless or a pain-in-the-ass. You constantly have to bail them out and fix things for them. They seem utterly incapable of taking care of themselves.
But they are very good at looking cute, helpless, and defenseless, and thus appeal to some inner need we all have to nurture.
The problem with being a Sparkle Pony is that eventually, people get tired of your "Perils of Penelope" scenario, where you constantly have to be rescued from one situation or another - just as they tire of the Friend with the Perpetual Problem. And over time, you will lose your allure of helplessness and cuteness, as a layer of crass manipulation reveals itself.
It is a far better approach, I think, rather than to rely on others to bail you out, to try to fend for yourself. Frankly, it often is a lot less work.
The problem with having Sparkle Ponies in your life is that they often take up a lot of your emotional energy, time, money, and physical effort. And while you may have a natural desire to "help those in need" - this desire can be hijacked by a Sparkle Pony in short order.
Sparkle Ponies are pretty. Sparkle Ponies are fun - for a while at least. But they are best viewed from a distance, I think....