>>38184516I wouldn't say that the mane6 are completely unique based on their general traits but the nuances and details that were included in their characterization make them stand out a bit more, both back then and even now.
Ponk can be compared to a lot of other comedic relief characters. Her extra cartoon-y movement and animation, her cheerful attitude, the 4th wall breaking jokes, her loud (and some would even say, obnoxious and annoying) mannerisms, etc. those have all been done before and after. As
>>38186776 pointed out, the 'randumb' character is something you see a lot. These kinds of characters are usually quite popular with kids and Ponk is no exception. Sadly, they tried to steer her more into that archetype and lost a couple of things that made Pinkie unique along the way, though I wouldn't say that she lost all of her personality.
I feel that Pinkie stands out due to a few traits; her unrelenting desire to befriend and brighten the days of almost everyone she meets and the lengths she'll go to achieve that, just how little malice she exhibits overall and her insecurities, to name a few.
The first one is fairly self-explanatory. I can't really think of many characters that rival her commitment to making people smile and be happy. This is actually where one of my favorite things from the later seasons comes in. The fact that Pinkie rivals Twi's organizational ability but only when it concerns people's party preferences, other related information and when she's fulfilling a Pinkie promise is such a nice thing for her to have and compliments her desires quite well.
Concerning the malice thing, I think I can explain it best using an example. In the first season's episode 'Griffon the Brush Off', it's shown multiple times that Pinkie gets 'pranked' by her own and RD's pranks but she never gets spiteful, frustrated or anything of the sort. She simply does her cute snorty laugh, just like she would've done if anyone else would've gotten pranked. Most other 'prankster' characters would absolutely get mad when those things happen to them but not her (or RD for that matter). The early seasons showcase this quite well.
Her insecurities combined with her other traits are also quite neat. Not necessarily unique, but utilized well. Because we know just how much friends mean to her and how much she does for them, it really helps sell her (somewhat literal) deflation at the prospect of losing them. Same with her desire to match her friends' expectations, even if it's just what she thinks her friends anticipate from her.
As a final point, I really like what they did with her family. It would've been so easy to squeeze out some drama by going the predictable route of Pinkie being ostracized from her family for being different and them later reconciling, etc. The Pies fully supporting her and being on-board with her antics from day one is vastly superior to any of that. It's super cute and I'm so glad they did it this way.
