You were the first hybrid ever created. There were many things about you that were different from the commercially bred versions that came after you, but first and foremost was the little-known fact that you were immortal. You have outlived anyone that knew of your existence and every single owner that ever took care of you. Because you found loneliness to be worse than the pain of watching yet another owner die, you let yourself be adopted yet again. But as the years flow by and your latest owner has yet to show a single wrinkle or sign of aging, you begin to wonder if they might have a secret of their own.
(( I personally pictured this as a hybrid and vampire story, but feel free to tweak to your hearts desire ))