A character has an old robot and deliberately keeps it despite new models being around. It can be done for practical reasons or just to save money. If it's not, it's always a trait of good characters or, when villains do it, a Pet the Dog kind of trait. This is often An Aesop (and not even a very hidden one) where the old robot will be shown to have a much more developed (and human-like) personality, while the new models will be more able and better looking but unfeeling. Examples of Good Old Robot include: