A medical Plastica that was going to be thrown away for his uselessness, he was rescued by Dorothy who exchanged one of her eyes for him. Given the name Ponkotsu, he is now Dorothy's master and lives with her and Rodbart. Because of him being a medical Plastica, Ponkotsu is nearly useless as he can not lift heavy things. Strangely, even though he is a Plastica Ponkotsu displays an array of emotions.
There are hints that Ponkostu killed someone before and he himself also confirms this.