Alright, everypony, I'm a noob with only about a week and fifteen episodes of experience, but I've learned a lot in that short time. You see, within a day of catching and accepting the addiction, my computer crashed and sent me spiralling into cruel withdrawls. I often watched the single DVR recorded episode I had three and four times in a day, but it was never enough. I had a lot of time to reall think about why the show had such a tight grip on me, why watching it made me FEEL the way I do. What I've done here is compiled all the reasons that I believe to be the secrets of MLP:FiM's charm, as well as some of the more profound psycological effects it has.
I will begin with the simplest of reasons, the one you'd most likely use to convince a freind to join the herd: The show is actually good.
Simple, yet undeniable, the writing, art, and animation of the show make it excell in every technical way possible. One thing I've noticed in specific about the writing is that unlike most modern shows that make departures for ironic effect, My little pony adheres to honest morals and satisfying conclusions. You see, in cartoons like "regular show" and more recently, "The amazing world of Gumball," characters blatantly behave in annoyingly immoral ways for the sake of a quick joke. Whlie characters should have flaws, it also seems like those kind of characters never grow or progress throughout the episode, and they often end up with more conflict than in the beginning (for irony, agian...). In MLP:FiM, however, characters actually work through all major flaws, resolve all conflicts, and actually create a solid sense of closure.
Next, Is the rebellious aspect. While many trolls unrightfully assume this to be a Brony's only motivation to watch the show, there is an undeniable appeal in being able to say "What's that, society? You say I can't watch ponies? Well, try and stop me!" What's dangerous about this, of course, is when the non-believers think the show is just an elaborate trolling.
Increasingly more complex, is the appeal of the MLP community. I've met a few Bronies back in my home domain of "Teh Flood," and from my experience, I have yet to meet a Brony who isn't polite, welcoming, and entirely upbeat. Anyone would find comfort in the idea of having a few million people out in the world who, with the exchange of a single reference, are instantly a freind of yours. Couple this with the novelty of converting your IRL freinds with a zombie horde-like mentality, and the allure of the herd is one few can resist.
Finally, there is just something profound and strange about ponies that will be difficult to explain. Before I was ever converted, I saw it in other Bronies: they were just more optomistic, more happy to be where they are, as if they'd stumbled on the secret to the universe. It's not so much a reason that makes the show epic, It's a feeling. This feeling, while hard to explain, is the core that makes the show so addictive. Some say It's lightheartedness, and not caring what the world thinks, others say it's almost nostalgic, like childhood, or like getting back a part of yourself you had to leave behind. Whatever it is, once you taste it, you need it just to feel like a whole person, and this is what makes the show so addictive.
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It shows us what a better world might be like. Not some politicized "utopia", afterlife "paradise" that sounds like good news at the moment but'd suck to actually live in, not some scifi wonderland showing of how awesome things'd be if we just had this gadget, or any other of numerous similar trappings. No, just a world that'd *actually be nice to live in*, a glimpse of what life might be like in an universe that wasn't cruel. Not flayed and put on display, but shown as a background assumption, the way it'd actually appear to someone who lived it. Goodness in a pure independent form, not reliant on contrasting with something bad making it stand out.