This is going to be sort of vague. This morning I was thinking about what the Perfect Octopus would be like, but I don't think there really is such a thing. Obviously it must have eight arms, but merely having eight arms is not sufficient for a thing to be an octopus (or even necessary) and octopuses come in many varieties. There is no one single canonical octopus, to which any entity can be compared to determine its degree of octopus-ness.
There are, though, some properties that are like that. This example is not perfect, but it gets at what I mean: to what degree is an entity Kafkaesque? There is only one way to decide, and that is to compare the entity with the works of Kafka. Opinions may differ about how strong the resemblance is, but the works of Kafka are the standard, and the only standard. Any other proposed standard has authority only by transitivity. And if the works of Kafka aren't themselves Kafkaesque, then nothing is.
In some ways, the International Prototype Kilogram is an extreme example of this: an object has a kilogram of mass if, and only to the degree that, its mass is equal to that of the IPK. But in other ways this is not at all the example I want. My great-uncle's graduation ring is not a kilogram, even though it closely resembles the IPK in being roughly cylindrical, mostly made of platinum and residing in Grenoble.
What I'd like is to find classes of things that are defined by their overall similarity to a single prototype. So far the best example I've thought of is a Hitler mustache. I'd prefer an example that wasn't associated with an individual person, and very much prefer a non-Hitler example.