Since this group is all about the hidden depths of characters, perhaps it would be a good idea to start a thread to discuss those hidden depths. Many of the characters can be portrayed as simple one dimensional characters through their actions and reactions, but it's through the exploration of the deeper histories and the reasons for those actions and reactions that we find depth.

I use a simple system for characterizing any character that I take and shape.

First Dimension Surface traits, surface reactions. This is the character's 'public' face. The face they put on when they are just living life, day to day. This is what we see of most of the background ponies and side characters. We don't spend enough time with them to really explore beyond the surface.

But. Surface traits are often a counter or a complement to other traits hidden beneath the surface.

Second Dimension Surface traits can be used to cover deep fears, or inner demons, that haunt a character. Pinkie Pie is an amazing example of this. She is bubbly, hyperactive, and super outgoing. But when she's pushed into believing that her friends don't want to party with her or even be around her, we see her greatest fear: she's afraid of being alone. So much so that she creates an imaginary set of friends to have a party with. She so deeply ingrains this that she can't see when Rainbow is trying to tell her otherwise. She's afraid of being sent away to be even more alone. Later, in Pinkie Pride, we see this turned around. She's afraid of being left out, but then she picks herself back up. That's growth.

Third Dimension Real Character. This is what comes out when a character can't be pushed any further. Going along with Pinkie Pie, I would say that Pinkie is determined when she's pushed. She doesn't let silly things like physics, or logic, or a friend's honest attempt to bring her back to the real world, stop her from going in the direction she's going. Not until she realizes it for herself.

This is not necessarily a classically 'good' character trait. But it is a real one. She's stubborn when pushed too far.It takes the realization that Rainbow isn't having fun in Pinkie Pride, and it takes the realization that her friends really do care for her in Party of One to stop being a pessimist.

This brings us to backstory. All of these come from someplace. I think that the final two, determination/stubbornness and fear of being alone come from her life on the Rock Farm. She was alone much of the time, it seemed, moving rocks from one place to another. It's not a life she wants to go back to. The one bright spot in her life was her family. And her family appears to be a very slow to change, very stubborn bunch of ponies. Her surface traits then, are a real part of her, but they're also covering her fear of being alone.

That's the system I use, with an example. Anyone else care to chime in with your systems of characterization? Thoughts on other ponies and their three dimensions of character?

What a happy coincidence, I was actually working on my own post with a set of examples!

Now, when I say hidden depths, I mean that the reader is given new insights into the character, and the character is given motivation for their personality & actions, more so than they usually get from the fandom.

This could be an explanation for behavior they've shown in canon, or even just having them do something other than the running gags they're known for; especially if it's a logical extension of their established traits.

For example, this would be a shallow character:

"Ew! Dirt!" Blueblood flailed his smudged hoof and cried like a baby, because he's Blueblood and that's what he does.

This has Blueblood freaking out because... because he's Blueblood. No explantion, no reason, it's just the way he is.

A slightly better character would be:

"Ew! Dirt!" Blueblood flailed his smudged hoof and wailed, because like any of the snobs from Canterlot, he was totally unprepared for the realities of life.

This gives Blueblood more character since it gives a reason for his actions - he's a product of his culture. He comes from a place where this behavior is accepted, normal and reinforced by every pony around him. This isn't a great characterization however, since it's not personal to Blueblood. It shifts the generalization up a level to "Blueblood is freaking out because... he's from Canterlot."

A character with hidden depths would be:

"Ew! Dirt!" Blueblood flailed his smudged hoof and started hyperventilating. He was in Canterlot. He wasn't in the Everfree. He was safe. He couldn't hear the timberwolves closing in. He was safe. He wasn't a helpless colt, lost and alone. He was safe.

This gives a reason and makes it personal. Blueblood is freaking out because... he had a traumatic experience when he was young, and it's still affecting him to this day. It's not arbitrary, like he woke up on the wrong side of the bed that morning. It's not temporary, like he had new shoes. It runs to the very core of his being and is fundamental to how his character would act.