Edit: I didn't know you could do a back story, so here it is for Radio.
Radio Active, a self named pony, lived and grew up in a dumping site for bio hazardous waste (Hey, Pony ville has to have at least one of these somewhere, you can't expect them to make all of those things which can float in the sky and such, and not get any waste). She has been there for as long as she could remember, and probably some time before that as well. There were other ponies that lived there at one time, most of them die off in a matter of days. It is quite a wonder that Radio didn't, considering she was merely a baby at the time. Most of the ponies that she sees dies in a few days, there are even some of them that dies as she watches helplessly. She grew up in a solitary environment where she had little to no contact with other ponies, and pretty much no info about the world outside of the junkyard. She never made an attempt to leave since she had seen acres upon acres of land and she couldn't even see where the pile ended. She tried to walk to a point where she would be able to see where her world in the junkyard ended, but after walking until her hooves were sore and she still couldn't see where the pile ended, she gave up and never tried to leave again. That is until she realized she had started to grow wings.
Radio was an Unicorn, she could remember using magic since day 1, so she was shocked when she suddenly could feel her moving something on her back. After living in the junk yard for so long, the bio hazardous waste had finally done something to her other then create strange markings on her, wings had started to grow on Radio's back, and her horn had started to become sharper on one side like a blade. Her cutie mark came around this time. She wasn't paying much attention to it since she was so focused on the new wings on her back. The first time she had tried flying she had fallen down into a puddle of goo, so did many of her other first attempts. When she wasn't practicing flying, finding food and water, or taking a rest, she would look around the junk yard for usable things. Her favorite thing that she had found was a pair of old style headphones, and a Mp3 player that still worked, even though it only had 5 songs on it (Her favorite was a song called RADIOACTIVE). She tied it to her leg using a rope she found. on the other side was a knife, which she usually used for cutting cans open.
She does manage to leave the junk yard... but not the way that she wanted to have left.
That is sort of how I thought Radio would had grown up as I was making her, of course, you can ignore it and just make up another one. I also want her to like my other pony, of course you can ignore that too.
