Consider – Huxley: The Doors of Perception first person shooter MMO.
Background: This short book from 1954 was one of the earliest explorations of experimentation with mescaline and LSD. Aldous Huxley discusses his experiences, results, perceived dangers, and perceived values from altered states of perception. Huxley got the title from the William Blake poem, The Marriage of Heaven and Hell, and the 1960s psychedelic band The Doors got their name from Huxley's book because of the influence it had over Jim Morrison, and it had a huge impact on culture in general and the drug culture of the 1960s and 70s in particular.
Now imagine a first person shooter MMO based off of that.
Newbie Zone: upon entry, the player picks up his flamethrower and ingests powerful hallucinogens.
Objective: melt your enemies' faces off before your own melts off.
The Woodstock zone: upon entry, the players are told to find the brown acid and destroy it before Carlos Santana's epic guitar solo.
Objective: defeat zone boss Abbie Hoffman, who is invincible unless you can convince The Who's lead guitarist Pete Townshend to smack Hoffman in the face with his guitar as Hoffman attempts to cut the guitarist off to make an announcement (this really happened).
The Doors raid: to gain access to this level, players must be keyed by lighting Jim Morrison's fire in order to Break on Through to the Other Side. Once on the Other Side, players will discover both that People are Strange and will continue to be so until the team fights through the Riders of the Storm to get to the boss mobs.
Objectives: find (a) a killer, whose brain is squirming like a toad (because it turns out, it is a toad), (b) a Twentieth-Century Fox, and (c) Mr. Mojo Risin' and defeat them. Players complete the zone by freeing the toad back to his lily pad (at which point it become a Peace Frog), sending the fox back home, and returning Mr. Mojo's magic to the Lizard King.
The Parliament-Funkadelic zone: players are denied entry until they can prove that they've got The Funk slotted in the Trunk space of their inventory. On entry, players are approached by quest giver, bassist Bootsy Collins, who enlists the players' help in attempting to free the captured Sun Ra from the forces of a group known as the Placebo Syndrome, led by Sir Nose D'VoidofFunk.
Objectives: Players engage in a series of quests along side Aquaboogie soldiers to prove they are under the One Nation, obey the Law of Supergroovalisticprosifunkstication, and to collect scattered pieces of Funkentelechy until they have enough power to charge their Bop Guns for the assault on the Syndrome Dome, the Zone of Zero Funkativity (aka the Nose Zone). Once Bop Guns are recharged, the players work with the Mother Ship to drop Da Bomb on the dome, tearing the roof off the suckah and face D'VoidofFunk's troops in the Nose Zone. If they succeed, they free Sun Ra from his Placebo oppressors to reunite him with the Arkestra.
The Jefferson Airplane zone: Players may enter this zone after taking the pill that makes you small. Once small, players will chase the white rabbit past the hookah and into a tea party, in which the players engage in puzzle solving and light combat with the Mad Hatter and the Cheshire Cat over tea.
Objectives: eventually, you must ignore the Mad Hatter, fight your way through the chessboard, work through the White Knight's backward talking, defeat the Red Queen zone boss, and escape through the looking glass, only to discover you're now fighting blue monkeys in the Emerald City and have somehow wandered into the wrong book. At that point, you become lonely and are asked Don't You Want Somebody to Love?
And so on and so on.
I think a game like this would definitely be revolutionary in the MMO genre, and if it became popular, would most likely make ESRB long for the days of mere excessive violence in online gaming.