Living Fiction - Identifying an unrecognized genre of fiction/literature

There is a type of fiction or literature that seems to have a life of its own; it is not confined to page or stage and it is a common part of human culture that we are all familiar with but is not recognized as a genre of fiction like Drama, Poetry; Prose or Song.
Examples of it are Santa Clause; Gremlins; the Easter Bunny; The Sandman; The Bogeyman; The Tooth Fairy; The Man In The Moon; a childs imaginary friend; Old Father Time and the Loch Ness Monster
Living fiction is when we talk of a fictional character as if they were real and walking about in the world and they are alive for another reason, because we are constantly adding to their story and giving them new characteristics.
You may say, "That already has a name. Its called a mythical character".
But an imaginary friend is not a mythical character and the Tooth Fairy is not linked to any myth or religion the way that Thor or Hercules or Samson is.
So if you cannot fit Gremlins; the Loch Ness Monster and a childs imaginary friend under the label of Myth then what label can you give them that adequately describes them all?
What do they all have in common? They are fictional and we pretend that they really exist; that makes them a type of fiction or genre but one that is distinct from other types of fiction.
Ofcourse these characters can exist in other genres of fiction; we can write a story or a play or a poem about Santa Clause but when we are talking about Santa Clause as if he really exists he is not then a character from a play, story or poem; he is something else, something which, because we give life to these characters, I have called living fiction.