Any fictional Spec Series?

Mar 21, 2014
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Wondered if there are people who participate in any fictional "spec series"?
Corvettes for Corvette Series?
Or Porsche GT3 in a Porsche Super cup type series?
Or any of the cars available.
I think I remembered seeing a Audi 90 Quattro single race being talked about, but not a proper series of say 15 tracks or something like that.
Is that the territory of clubs and leagues?