Hmm, this is an old thread. I guess I am bumping it. The character that experienced the greatest growth in my opinion would be be Rarity (Pinkie Pie is a close second, but that is neither here nor there). This is a bit of a long post, I guess. But I have to explain my decision somehow, right? At the start of the series, Rarity was displayed as prissy, dramatic, selfish and vain. She even seemed a bit catty and arrogant in Look Before You Sleep. I believed that her character was quite shallow. That is, until we arrived upon the Diamond Dog episode. It was then that you discover that she is not just pretty, but also intelligent and witty. This really caught my attention, as she did not seem to be an interesting pony prior to this. No, her "Art of the Dress" song hadn't won me over, but that whiny performance sure did (hehe, it still makes me chuckle). Fast forward to S2, and we get Sisterhooves Social. This is where I found out that she is not only smart and beautiful, but she has quite a range of emotion. Here, she has been angry, regretful, jubilant, helpless and forgiving. Seeing her interact with her sister really showed how her big head can sometimes get in the way of her big heart, though the latter eventually outshines the prior. This thought is reinforced in Sweet and Elite. She has a pattern of recognizing she's in the wrong, taking the responsibility for her actions and then fixing them as best as she can. Continue to watch, and we get episodes like The Secret to my Excess and Putting your Hoof Down. In these episodes, we see her warm heart glow even brighter. In TSTME, she appreciates the fire ruby that Spike had given to her, but what she truly cherishes is the display of generosity and kindness. She did not let the big dragon take it; not because of how pretty it was, but because of what it meant to her. Another display of thoughtfulness is when Spike believes that he is going to fall to his death with Rarity, he almost confesses his admiration for her. However, Rarity thought of him first and made sure he held on to his dignity (although she generally loves to be loved). In PYHD, we see that she tried to help Fluttershy long-term by giving her a shopping technique. When Fluttershy insults Pinkie, Rarity sticks up for her, and dis-encourages the obnoxious behavior. Even when she is insulted herself, she is hurt, but sets that feeling aside so she can be empathetic for Fluttershy. Then she tries to console her and try to detour Iron Will from entering her house (since he was after Fluttershy while she was in an emotional state). All of these things lead me to believe that she is a compassionate friend. So in conclusion, what I originally thought to be a very self-absorbed character, beautifully blossomed into an intelligent, emotional, responsible, thoughtful and loving individual. I suppose looking back on all Rarity-featured episodes, I can see these character traits... But it was only when the series progressed had it become extremely apparent to me. I am so pleased to have a stereotypical "pretty girl" (or pretty pony, in this case) not end up being the antagonist or *****y sort. Instead, she is a wonderful role model. Not only does she teach children and adults alike not to judge a book by it's cover, but she also displays what it really means to be truly beautiful. TL;DR-- Rarity seemed pretty darn shallow at the start. Selfish, vain, rude, ignorant, etc. As the series continued, her good intentions and compassion become more obvious. Her character development shows that Rarity is not only beautiful on the outside, but on the inside as well.