Nothing is known about Percy's past before he was Bio-Fused into an Avonside saddle tank engine. He did not survive his Bio-Fusion process and he was put on display during the off-season with other failed Bio-Fused experiments that were too unwell to work or already dead like him. While Percy was on display, his eyes rolled into the back of his head, and his skeleton tilted out of his artificial frame, making his face turn to the side causing blood to spill from his smoke box.