Detective Erin or Erin for short, is a detective famous in Ponyville and Canterlot for his infallible nature for crime solving. When Changelings were unreformed, he found a changeling pod in Canterlot and took it in to his house and it hatched into a unreformed changeling. He raised it from right and wrong, despite it being vicious at times. When the changeling was reformed, he became loving of every type of pony and every type of creature. Erin named the Changeling, Coldy Stone and adopted it as a son.
Erin is a white pegasus with brown mane and a brown tail, and red eyes. He is also the leader of a Detective Agency that he owns, having 3 other very skilled detectives with him. He is known for being formal, mission focused, and vigilant at all times. From his father, he had extensive training in martial arts and he uses his martial arts moves to restrain criminals and arrest them. Despite that, he would tend to solve problems with diplomacy. For example, if two ponies were arguing with one another, Erin would step in as a moderator, and guide the two ponies to a mutually beneficial outcome. Another example, if a pony was robbing a shop, Erin would try to use persuasion to convince the robber to rethink his actions, or if all else fails, restrain the robber by force.
At the time of Coldy's bullying, Erin felt terrible to see his son get harassed daily so, he managed to get his son to be transferred to the School of Friendship. However, the celebration didn't last long since Erin and his detective agency had to go to Mount Aries for 'Important Family Business' that they couldn't disclose. They went their separate ways, Erin left with his team to Mount Aries, and Coldy went to live at the School of Friendship until either Erin came back, or until further notice, all dependent on Coldy.