Kingdom Of Loathing.
The Grim Fairytales are not part of the main quest though - you need to purchase (with in game pretend money - not real money) an item to play it. If you do play, you need to buy a grimstone mask from the Mall. At the time of writing, the cheapest seller has 48 in stock for 2,400 meat limited to one per day. You can earn this in about 20 turns for a brand new player, or a single turn if you're an old player.
On the other hand, the whole game is like that, so you don't need to wait until you can afford extra content.