Highly amused, I decided to write my own. Except the BoM ones at the bottom were written by Barb, and I just polished them a bit.
Warning: There are, of course, some real spoilers here. But if you haven't read Peter Milligan's ENIGMA, which you may want to do (I found it worth reading), you may not want to read its super-condensed version below, because it'll REALLY REALLY spoil it for you. On the other hand, I showed it to two people who hadn't read it, and they were so intrigued, they decided they just had to run out and read it. So decide for yourself first.
If that doesn't bother you, go ahead and enjoy.
GREEN LANTERN: MOSAIC
John Stewart, the African-American Green Lantern: Guardians of the Galaxy, why are you keeping towns transplanted from all over the universe here on OA?
Guardians (enigmatic): You tell us.
John: Fine, be that way.
John: I love music. And architecture. But I have a lot of anger issues.
[John learns about what makes sentient beings tick.]
John: You're running an experiment, using these alien towns as a microcosm, to see if, once you use the GL Corps to bring order to the galaxy, the different alien races can learn to get along on their own, without someone forcing their good behavior all the time. That's it, right?
ALAN MOORE'S BATMAN: THE KILLING JOKE
Joker: THIS'll get me some attention.
(Shoots and paralyzes Barbara Gordon, takes pictures of her suffering, torments Commisioner Gordon with them.)
Joker: You know what? We're both kind of crazy. It's so absurd, this thing you and I are in together, this relationship or whatever it is, it's actually funny when you think about it.
(The Joker tells a dumb joke. Batman and the Joker share a good hearty laugh together.)
GRANT MORRISON'S ARKHAM ASYLUM
Batman: What's up, Doc?
Doctor: The lunatics have taken over the asylum. The new head of Arkham's been trying some radical therapies... now he's trapped inside somewhere.
Joker: You better run, Batman, we'll give you a little head start.
(Batman enters the maze that is Arkham and whups up on various classic inmates mano-e-mano. He eventually reaches the secret basement of Arkham and learns that the man who built Arkham used quasi-Lovecraftian geometry to do so and thus the whole place is just chock-full-o-madness.)
Batman: Well, I'm ready to leave now, anyone wanna stop me from rescuing the hostages and leaving?
Joker: Nah, what the hell, go ahead.
PETER MILLIGAN'S ENIGMA
Narrator: Here's a normal, boring guy. But somehow these weird super-villains keep showing up around him. And lizards. And this superhero, The Enigma. It's like these comics he read when he was a kid. Let's watch this loser quest to find out what this is all about.
[We do so.]
The Enigma: I'm a weird mutant with amazing powers. My dad threw me down a well when he noticed I was a freak. I lived down there with just the lizards to keep me company. I evolved some of them with my powers. Later, I found your old house, boring guy, and read your comics and stuff. I became interested in you, so I thought I'd draw from the mythos of those comics to sort of try to...
Boring guy: Yeah, what was this all about?
The Enigma: Well I'm bad with social skills, so I guess this was my way of saying... I need someone to save me, too... I guess it was my way of saying I... kind of like you.
Boring Guy: Er... I'm straight.
The Enigma: Hey, if I can make lizards fly, I can change your lifestyle-- poof!
Boring Guy: Hey, you're pretty hot yourself! When I think about my ex-girlfriend, being the boyfriend of the world's only superhero sounds pretty good.
The Enigma: Yeah well this is great to finally talk and stuff, but my mom's come looking for me, and I'm scared of her. She's like me, but weirder.
Freshly-Gay Guy: Well, let's go talk to her. Maybe this is the light of new love, but I feel sure everything will turn out okay.
Narrator: And that's just what they did. I'd love to tell you more, but that's all I know. I, your narrator, am a talking super-evolved lizard! Betcha didn't see that one coming, eh? Eh?
PETER MILLIGAN'S SHADE, THE CHANGING MAN
Shade: Hi, I'm from another dimension or something. I traveled here with this amazing jacket, the M-Vest.
Kathy: It sure is weird how you jumped into the body of the homicidal maniac who killed my parents and my ex-boyfriend.
Shade: Well, he was done with it, getting the electric chair for his crimes and all.
Lenny: Hi kids, I'm Lenny, and I'm a hoot! And really funny! A girl called Lenny, is that droll or what? And I'm kind of gay! Let's us three go have crazy adventures where we quest for the twisted heart of America! It'll be like FEAR AND LOATHING IN LAS VEGAS only with the whole country, and instead of drugs, we'll just have Shade's weirdness!
Shade: Sounds good.
Shade: Damn... The dark heart of the American Dream is REALLY dark and twisted. I had to smack it down.
Lenny: But that doesn't mean the fun has to end, right?
Shade: Don't see why... let's open a weird hotel where weird people can come to us for a change.
Lenny: Why not!
John Constantine: Hey there, just passing through. Say, that Kathy is one sweet bird. You're lucky, mate.
Shade and Lenny in unison: Thanks!
Shade: Uh, oh, the weird beings that run the M-Zone of madness that sort of powers my M-Vest who set up this whole hotel thing have killed Kathy! I must pay them back for that!
Shade: Maybe she's reincarnated somewhere.
Lenny: Sorry, Shade, the fun's over.
Shade: No, come on. Let's try to recapture the wackiness for another 25 issues or so.
Reader: Oh, come on, just get it over with.
Shade: Here's the reincarnated Kathy. I think I'd better just settle down with her quietly and happily before the story takes another mistaken, terribly wrongheaded turn.
Lenny and The Reader: Yes, please!
MARVEL'S SECRET WARS (I)
Beyonder: I am the Beyonder. I'm all-powerful. I've been watching this universe for some time, and I'm blown away by this whole concept of "conflict" you've got here. I think it comes from this "desire" thing. Let's have you superheroes and supervillains and mutants and Galactus and everybody fight it out on this planet over here. Whoever beats everyone else, I'll give you whatever you want.
Heroes: We must stop them!
Mutants: Whom can we trust?
Galactus: Hmmm... this planet here? Just let me set up the Cosmic Pic-a-nic Basket over here... I just need to plug in the Cosmic Forkulator and the Cosmic Spoonitron... be right with you...
Doctor Doom: Okay, I'm in charge. Here's the plan: I've got to set up the endgame strategy. Don't let them bother me. Mess with them as you like-- if they come over here, cream 'em.
Other villains: Check.
Colossus: I fell in love with this alien girl, but now she's dead! I have no arousal for the barely-pubescent wiles of Kitty Pride anymore. Love sucks.
Sue: Reed, you mean that you've discovered that The Thing's orange rocky form is psychosomatic, and that if he wasn't so psychologically messed-up that he could change back and forth at will? What will we do? If we tell him, he'll be more mentally tormented than ever!
Reed Richards: Um... let's tell him it's just a weird side-effect of this planet.
Spider-Man: Hey, this nifty machine replaced my old torn-up red-and-blue costume with this spiffy black and white one! It makes its own webbing and fits me perfectly! Nothing bad could come as a result of this alien costume!
Captain America: This has gone on long enough! Let's end this!
Captain America: Huh. Doom is just an empty shell of a man.
Reed: He tried to take the Beyonder's power for himself. Got greedy, just like always.
Doom: Fooled you! I GOT IT!
[Doom kills everyone]
Doom: Who needs to win if you got da power, chumps?
Beyonder: Uh... this didn't turn out like I thought.
[The Beyonder brings everyone back to life. Doom is defeated.]
Beyonder: So, I declare you guys the winners. What you want?
Everyone: Just put everything back like it was, please.
Thing: Except me, I'm staying here! I can change at will here!
NEIL GAIMAN'S THE BOOKS OF MAGIC (4-ISSUE MINISERIES)
The Phantom Stranger: You're the greatest magician ever, Tim Hunter! Come and learn about magic, and sort of symbolically take the place of the reader in wonder and child-like amazement!
Tim: Yes, why not.
[Tim gets an owl and sees the start, middle and end of the DC Magical Universe.]
Tim: Well that was sure something, but I think I'll pass.
Phantom Stranger: Too late, you said yes.
Tim: Bugger. Oh well.
BOOKS OF MAGIC: THE SERIES
Tim Hunter: Well, so what now?
John Constantine: They try to milk you for all you're worth, kid.
Tim: Er... but am I still the greatest magician ever?
John: Tell that to this kid in this fantastically popular series of children's books who looks suspiciously like you. He's got a neat school to attend and learn magical stuff. And he has friends, unlike you.
THE NAMES OF MAGIC
Tim: Er... I can go to magic school, too! And I can get some friends!