[quote=gamer5]
No you can use both character which come from the RP's Earth, Characters from Mythology, Crossover Character and Original Characters (no matter if they come from a Crossover setting or your own).It is just that a more widely known character would be more powerful.
[/quote]

That doesn't really answer the question. The question was whether the characters are treated as being fictional within the universe that the RP is set in.