Okay, the revamped Filly board seems to like swallowing my posts, so I'll put it here. This is a thread for discussing ideas, predictions, and hopes for the cast of the series.
Rose: she kind of sounds like Starfire from Teen Titans, so I'd expect friendly, even clingy, and very knowledgeable on things 'normal' Fillies do not know much about. Wears her emotions on her sleeve, but doesn't break down into tears or nerves, unlike some main character unicorns I could mention.
Lynn: adventurous, but a loner. Likes to explore things on her own, some confidence issues but they only show when she has to perform. Not so much the first Filly to dive into danger as she is the only Filly who'll go into a dark place where others do not.
Bella: guessing she'd be sort of the Pinkie of the gang. Very extraverted, very excitable, but at her core she's basically a bird-talking hippie. The really innocent one, the idealist who wants everyone to be happy. Sort of a blend of Fluttershy and Pinkie Pie, leaning slightly more towards the Pinkie side of things.
Will: the prankster and goofy one. Extraverted, very much a performer. But what sets him apart from the usual examples of the archetype is the fact that he's so damn friendly about it. Hard to put off-balance, mentally or physically, first one to dive into danger, first one to shrug and go 'oops' when things go awry.
Cedric: more of a bookish smart than Rose, better schooled on things that normal Fillies can be expected to know. Rose knows some things about what other Fillies don't know. Cedric knows everything about what other Fillies do know, sort of. Introverted, not one to make a scene, very much aware of his own flaws and ambitions. Not the tuype who'd go and ask help easily, but the type who's easy to approach and always willing to help. I'd imagine there's some element of 'Yeah, I'm royal, but I'm still a student here' with Cedric. We might even get an episode where he has to tutor someone.
In terms of group dynamics:
Just for design's sake, half the cast would be extraverted, half introverted, with the main character somewhere in between, though what we've seen suggests she's leaning on the extraverted side of it. Lynn and Cedric are, to me, the likely introverts right now, and Will and Bella are obviously extraverted, based on the trailers. Rose has both the 'friendly' monicker and the apparent clinginess in Episode 4, but she's also supposed to be a painter, which would suggest she at least knows the value of silence and/or concentration. Unless she ends up being the van Gogh type whose insanity helps make her a better artist. That'd be neat, too.
Conflict-wise, inner conflicts would be:
Rose managing her desire to be close to her friends vs respecting their space. Wanting to help vs being a busybody.
Will wanting to show off his skills and have fun vs annoying and distracting his friends from important things.
Bella getting caught up in arguments and not wanting to upset either party. The basic conflict of any character defined by loyalty.
Lynn wanting to try things on her own, or fix things on her own vs acknowledging that she's just not capable of doing everything on her own.
Cedric coming to terms with the idea that no matter how hard he tries, he's not perfect and has to ask for help. The difference between him and Lynn in this regard is that Lynn actively seeks out challenges or adventures, where Cedric would find himself faced with them regardless of his actions.
As for outer conflicts, you can play out everyone against everyone if the situation calls for it.
Anyways, that's a first guess, maybe the toys have more information to debunk or confirm it.