Spark Sprint is a grey pegasus with glasses and black hair, with one of those "not allowed" symbol thingies as his cutie mark. This happened because he grew up in a place where nothing good happened, and he was never able to find a single thing to do. He soon realized his ablility to firmly refuse things without getting on anypony's nerves, and sadly enough that became his cutie mark.
Spark Sprint grew up in a place where it wasn't all sugar, spice, and everything nice. There were drug addicts, ponies involved with gangs, in short, it was a very bad place. Spark Sprint had to stay inside until he was able to move out once he was old enough to actually move out. He found he was able to firmly and angrily refuse anything negatively influental without getting on anyone's nerves, and that somehow became his cutie mark. Nopony else is quite sure why that would be a reason to get a cutie mark, though. After moving out to a better place, he had no intent to speak with any other ponies because his childhood was filled with violence. He mostly stayed inside all day and soon found interests in ponified versions of Earth television shows, such as "Doctor Whooves" and so on and so forth. Pretty soon he started leaving his house and soon enough became a well intented pony who went outside often and spoke with other ponies.