"What if ____ Wrote _____?"
That is, pick an author/writing style and make gentle fun of both them and the fandom by writing a story that's "Insert Author" writing a fanfic for "Insert Fandom." Or, writing like the "Insert Author" replaced the canon author of a particular fandom.
You know, like, you can have "Disney Writes The Matrix!" or "Dr. Suess Writes The X-Files!"
For an example, behind the cut is a ficlet I did for a similar challenge on Bloody Shorts. I can't seem to get the community linked right... augh!
Anyway, a sample of what I'm talking about is below.
In a great mansion in London lived people of a most peculiar sort. Above them all held sway a lady of great magnificence, whose hair shown like the star; Earendil, and she was the Lady Integra Hellsing, daughter of Arthur, son of the great clan that protected the land from Darkness.
In her realm, the Lady Hellsing kept two immortal beings of darkness. They served her and the cause of countrymen. Alucard had seen the rise and fall of many kings, and served the Lady well, being bound by an enchantment of deep magic. When fighting valiantly to destroy lesser minions of one of the great Enemies, he wounded a young maiden. Alucard took pity on her and held her to himself, whereupon he preformed the sacred exchange of blood to grant her the right to immortality. And he sang a song:
The shine of the moon and the dark of the night
Are gifted to the No Life King
Blood and wounds and lack of light
In immortal strength he sings
Will you not join me in this dance?
A pale and frail and mortal thing
Rise in power and in blood
And become a No Life King
The maiden, Victoria Seras, drank deeply of the blood of the mighty Alucard, and thus received his curse. Under him, she is bound to forever serve, as he serves under the Lady Hellsing.
Therein the mansion also lived a manservant, the true Sir Walter Dornez. He served his Lady Integra, and loved her well – and he did not fear the creatures of the dark that lived in the shadows of Hellsing’s realm, and he fought valiantly with threads that shone brighter than any gems that the great Dwarf Lords of old had ever mined.
Great peril befell the house of Hellsing often, and against the wicked Valentine brethren, Sir Walter, Alucard, Seras, and Lady Integra barely prevailed. All her brave soldiers dead, the Lady Hellsing hired warriors of another land, men who fought with courage and great honor.
As shadows grow when the sun dips down in the sky, a fear loomed over the house of Hellsing, like no other fear that had ever beset them. The valiant servants of Lady Integra learned that a greater Enemy than they had ever triumphed over before was rising in the land, an Enemy greater than the vile Southrons with their immortal swordsman. This Enemy used the wicked Valentines to breathe his name, a name that sank into the souls of the members of Integra’s Fellowship – Millennium.