Assuming Wikipedia actually performs this duty, that makes it a good way to answer the question of notability (as long as the investigating party is not an agent of Wikipedia, which creates an infinite recursion). If Wikipedia only runs notable things, you use Wikipedia to prescreen notability for you.

Theoretically being in Wikipedia implies notability; but not being in Wikipedia does not imply non-notability, only that nobody got around to creating a page yet.

Which is why we have pages like "List of recurring characters from Sonic the Hedgehog", naturally - http://en.wikipedia.org/wiki/List_of_recurring_characters_fr... .

At best, wikipedia editors may collect evidence for notability, but neither presence nor absence of a wikipedia page alone makes a strong case.

Notability is why we do have a page for them, instead of a page for each of them.