[quote=@Cuccoruler]
<Snipped quote by Rin>

He is tottatly a mythological creature! Wait, Or does he count as a god?
[/quote]

It is not a mythological creature.  Cthulu was created by H.P. Lovecraft, a fiction author, during the 1920's.  And as Roxas mentioned earlier, he doesn't want to allow famous fictional creatures that have no basis in mythology or legend.