Dungeons and Dragons

On Roundworld, a role-playing game where slightly nerdy humans assume the identities of warriors, wizards, thieves, elves, trolls, dwarves, etc, to solve problems and earn experience points - it is in keeping with their general unworldly nerdiness that this is experience gained in any conceivable world other than the one they actually inhabit.

(It is thought that The Colour of Magic originated from Terry Pratchett's experiences as a Dungeon-Master and some of the things he incorporated in the RPG group he ran - ie, the Luggage originated as somewhere to stash the loot but from which the loot could not necessarily be retrieved, depending on the beast's mood)

The younger vampires in Carpe Jugulum, have a similar sort of role-playing game where they take on mortal personas, for instance as chartered accountants called Nigel or shop assistants called Pam, and act out the problems and rewards appropriate to their characters. Younger vampires taking this game to extremes have been known to dye their hair mousy brown, attempt to drink wine, and most shockingly of all, to wear a lot less facial makeup, and wear colours other than black. This game is assigned no name but might well be called Htog.

In Sourcery, there is the character of Nijel the Destroyer, son of Harebut the Provision Merchant ("you have to be the son of somebody. The book says so"), who takes role-playing to its illogical extreme by actually seeking to become a barbarian hero. He is saved from himself by a combination of Rincewind's cowardice and Conina's despairing affection for him: it is a sad fact that a manual seemingly authored by Cohen the Barbarian called Inne Juste 7 Dayes I wille make you a Barbearian Hero!, which inspired his unwise career choice, is much more likely to have come from the fecund money-making mind of C.M.O.T. Dibbler, who is, for his sins, at least 100% more functionally literate than Cohen.