This is kinda like a Potter Law thread, but with the intention of focusing solely on a set of rules by which a crossover writer can observe to avoid the unbelievably common crapfests that are badly done crossovers. I'll start off with a few suggestions, others can suggest ones of their own, and dispute mine if they so wish.

Rule 1
There are always exceptions to the rule.

Rule 2
Do not cross over multiple characters. Especially: do not cross over love interests. So that means no Harry going to another fandom and a few chapters later Ginny catching up with him.

Rule 3
Do not allow your main character to cross back and forth between his or her original fandom and the one in which they find themselves.

Rule 4
Do not cross over in more than one direction. So, have Harry Potter in the Dresdenverse, or Harry Dresden in the Potterverse, but not both at once.

Rule 5
Choose your cross carefully. Some fandoms just don't go together.

Rule 6
Do not rape one fandom at the expense of another.
Exception: It's okay to rape Anita Blake.

Rule 7
Do not write a crossover for the sole purpose of pairing two characters together.

Rule 8
Keep your crossover limited. The more you try to integrate two fandoms, the messier it will become. The best crossovers are those that are kept separate but for a single point of contact: the main character.

Rule 9
Firefly is sacred. Mess with it at your peril.

That's all I've got for now. Your turn.

Interestingly enough, many of these rules can also be applied to time travel fics.

 

Haha. Should I be scared?

 

Woah, Bio gets banned and suddenly everyone's running to fill his shoes.

 

Wait Bio was banned when did this happen?

 

Rule 10:
Do not move someone between fandoms only to replace an existing character.
Example: Buffy dies in an accident, Harry moves to US, is secretly a girl, and becomes a Slayer.

 

You sir, have a sick and twisted mind to come up with such a disgusting plot line...

 

Rule 11:

Do not cross all the characters of one world with the world of the other fandom (without characters.)

Example: Harry, Ron and Hermione start their very own Pokemon journey. Dumbledore is a Pokemon Professor and Luna is a Jigglypuff.

 

Rule 12:

If you put one character into a different fandom do not change everything about them to accommodate the other fandom

Example: If for some reason you put Harry Potter into Naruto do not make him the ultimate ninja with three bloodlines and a demon. At that point not only does it suck but it ceases to be Naruto/HP and just becomes Naruto with a white Gary Stu

 

This could work as a corollary of rule 6 (or 12) but -

Rule 13:
Do not make the main character of the cross to be ridiculously over powered, kicking everybody's ass with a wave of his hand; but do not make the main character totally weak/emo/small either (This is done in order to facilitate a slash pairing mostly - like Harry/Kakashi).

 

Is he Banned banned, or I'llbebackinaweek banned?

Anyway, not sure how this would fit in, but I hate flashbacks to the original world, with all the left behind characters whining and trying to get him/her back.

 

Wow, back in the day, I used to write "how-to-not-write-crossover" things - specifically on anime series stuff. Let's see if any still apply here...

Here are some draft rules, integrate to the main list at your desire:
Rule J1: Watch your damn characters
Don't screw up the characterization of the characters of either series; but especially make sure you know the characters you are crossing into.

Example: (Harry Potter into the Chronicles of Narnia - by the way, don't do this)
Harry Potter looked around in confusion. Apparently he was in the land of Narnia.
"I'm Russian-French and a wise-cracking buffoon," pronounced Aslan in an annoying, squeaky voice.
"And I'm Father Christmas", yelled Edmund.

Corollary
And while you're at it, don't change the crossing over characters either just because they're crossing over.

Example: (Harry Potter into Mortal Kombat)
"Ha ha, I sure hate whitey!" Harry screamed effeminately, his deep red hair covering his four-armed muscular horse body.

Rule J2: Iceberg, Dead Ahead
Watch your damn ships. Just because there exists a hot female or male or whatever in one world is not an excuse to pair up someone. A bit of latitude for parodies here, but not much. Use some thought please.

Example: (Harry Potter into Batman: the Animated Series)
Harry grinned. "Oh, Poison Ivy, Batgirl, Catwoman, Zatanna, and/or others. You all sure are the sexy."
"Shut up and bugger me in an unconvincing love scene."

Rule J3: A Pebble in the River
When crossing over, don't just relive the entire crossed over canon with absolutely the same thing only with your crossing character just sitting there on his/her hands. We've already seem a billion Harry Potter fics that start from first year or before, and trudge through sludge to get anywhere. We don't need crossovers too.

Example: (Harry Potter into DragonLance)
Harry got a comfortable seat and watched about two hundred years of books. He yawned, and took a nap.

Rule J4: No Bloody Vampires
Don't cross over with Twilight, unless it is explicitly the following one line:
Harry appeared and destroyed everything and everyone involved with Twilight, from the characters to the author to the publisher to the movie director to the actors, then he left, never to return.

Rule J5: Don't Insert (Hey, this is a good point) Explanatory Author Comments
Seriously, that is just annoying. I think this might apply to all fanfiction, though. Hmm... Maybe I should move it.

 

I'd add:

Rule 14:
Crossovers should be stories first, crossovers second. They should have conflict, plot, and tension. Above all, there should be a point to your story. "Hey, wouldn't it be great if Harry got a light saber and learned to use The Force?" doesn't qualify.

 

Rule 15:

Do not use random portals through the space/time continuum that randomly spring up as your excuse to cross over two worlds. If you're going to use a portal, at least have a plausible reason for it.

 

My problem with crossovers has always been that I've no fucking idea what any of the references are when working with anyone other than Harry Potter.

Amendment: Portals are limited to female, gun wielding prisoners only. Only fags use something as contrived as a portal.

 

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Do you even read what you are typing?

 

I thought it was hilarious. Anyway.

Rule 16: Don't crossover into worlds that take place in the same "world" but have conflicting systems.

Example: X-men has a great story line, so does Harry Potter, sticking them side by side and trying to explain why wizards and mutants don't know about each other but have the same kind of powers has a 99% fail rate.

 

Rule 17: Don't cross over two worlds that have totally opposing systems of battle.

Example: Harry Potter, a practitioner -though a bad one- of magic, jumps into the world of 300 where the closest thing to magic is a bunch of men throwing flashy fireworks with shrapnel.

 

Aren't these called missiles?

Anyway Rule 18: Do not mix crack-like genres with serious one, unless you are looking for a strange an unusual crack fic. For example, while separately, Harry Potter and the Looney Tunes may be fun to read/watch, under no circumstances should they be crossed.

 

Looney Tunes is serious business.

 

Rule 19 Don't just assume everyone knows what you're on about when you talk technical details of your crossover. A little (well placed, well executed) backstory can go a long way to help your readers