Caveats

M. John Harrison is allowed to DM or play.

JRR Tolkien is allowed to play, but not DM, ever. Unless it's a module.

Fritz Leiber is allowed to play or DM, but he's not allowed to sit near any girl I'm sleeping with.

Michael Moorcock is allowed to play, but may only DM if he agrees not to re-use any NPCs.

China Mieville is allowed to DM but not play, and he can only DM if he doesn't do any of his own dialogue. He may write modules.

J.L. Borges is allowed to DM or play, but is reminded that monsters with infinite hit points are not allowed.

Patton Oswalt is allowed to DM or play.

Neil Gaiman is allowed to DM only if he can manage to get all the way through a session without having a monster tell you something that his therapist once told him. Which I'm guessing he's not. Plus see also Fritz Leiber, above.

Ozzy is allowed to play, but only if he agrees to DM at least once.

Thomas Pynchon is allowed to DM or play, but not tell jokes after the first drink.

The authors of the Elder & Younger Eddas are allowed to DM or play, but if they DM, they are only allowed a maximum of 30 NPCs at a time.

If Dorothy Parker is DMing, she will be held to a 2-drink maximum. If she's playing, she will be held to a 2-drink minimum.

All women are allowed to DM or play, except: Sarah Palin, Hillary Clinton & Lady Gaga.

Joan Rivers must play, but is not allowed to DM unless Oscar Wilde helps.

James Cameron is not allowed to play, but may be allowed to DM if we get to kill him.

Walt Simonson from 1983 is allowed to play or DM, if he wants to play now, we'll talk.

Franz Kafka is allowed to play, and will be allowed to DM if everyone at the table has had at least one drink.

Oscar Wilde is allowed to DM or play. He must play if Jack Vance or Michael Moorcock are playing.

Anyone who is both involved in the field of animation & Japanese may play or DM, but may not include romantic subplots or philosophical quandaries.

If Franz Kafka DMs & Oscar Wilde plays then...ok my mind was just blown, moving on....

If David Foster Wallace plays, no rules-lawyering & if he DMs, he is reminded that no-one cares about his goddamn potion-miscibility chart.

The authors of the Bible are allowed to play or DM, but are reminded that alignment restrictions will be enforced.

HG Wells is allowed to DM but not play.

Edward Gorey is allowed to play, but is only allowed to DM one-shots.

Jack Vance is allowed to play or DM.