Fan Casting No Full Name Given in Sort by Tropes

When a character is not given a full name, only their first or last. Often happens because of The Law of Conservation of Detail, as in many cases, it's easier for the writers to not bother including a full name, and the audience doesn't need it. It can also be that a singular name is more familiar to the audience, as usually people don't refer to others they know by their full names. One could compare this to First-Name Basis or Last-Name Basis. Unnamed Parent can also fall under this.