Changeling: The Lost has the Talecrafting rules in the sourcebook Swords at Dawn: characters can purposely force Tropes to occur at will because they realize their own lives work by the rules of stories. The book actually suggests TV Tropes as a good place to find examples of patterns to use!
Metagaming is actually an option for player characters in Grimm. The Gaming trait covers knowledge of such things as fairy tales, fantasy novels and films, fantasy card and board games, narrative video games, and the game Traps and Trolls. Since it covers not only knowledge of fairy tales, but things that are either directly or indirectly inspired by them, you can use this trait to cast or identify spells, recognize fairy tale settings or characters, and determine the weakness of fairy tale characters.