Pinkie grew up with a chip on his shoulder. Oddly enough, he didn't get the name because of his pink coat but because he was the runt of his litter and everyone said he was like a "pinkie finger." Being smaller than everyone else while he was younger meant he took a lot of s!t for no reason. He grew up hard and he grew up fast but one winter while everyone was hibernating something happened. He grew. When all his friends and family woke up that spring morning he was no longer the little guy. Now, coming out of the den with a new superpower (being bigger than everyone else) he did what every little guy who ever went through a growth spurt does. He became a bit of a ****.
Pinkie's newfound reputation led him to a lot of unseen problems. People missed the sweet young bear they lost the previous fall. It took a little time, but Pinkie learned that treating others the way he was treated and not the way he wanted to be treated left him feeling blue. And he wasn't blue, he was PINK!!! He forgave those who picked on him. Honestly, they were mostly from broken families and did a lot of drugs in high school and Pinkie learned to let that go. He decided the best way to move on was through positivity and love. This is why he shimmies so much, cause he's shaking that s!t off.
Now, you can find Pinkie getting down on the dance floor with a smile on his face, greeting everyone he meets with the biggest of bear hugs and spreading the love. Also, he's probably high.