Title: Crisis War Across Dimensions!

Main characters: The Mane Six, Spike, Tirek.

Genre: Crossover, Comedy, Adventure, Alternate Universe.

Crossover With:

Cartoon Network:
Dexter's Laboratory
Ed, Edd, & Eddy
The Powerpuff Girls
Samurai Jack
Ben 10: Omniverse

Nickelodeon:
Danny Phantom
The Fairly Oddparents
My Life as a Teenage Robot
Crash Nebula
The Modifyers

Note: This story shares the same universe as a "Double Rainboom", yet takes place sometime after Season 4(and Rainbow Rocks).

Premise:
When Rainbow Dash pulled off of the "Double Rainboom", she had no idea that when she broke through the boundaries of her own dimension, she ended up causing a distortion within the boundaries between other dimensions as well...

This distortion catches the attention of Aku, the shapeshifting master of darkness, who proceeds to use it to his advantage and look into other dimensions, upon seeing so many powerful heroes across the dimensions, he then proceeds to recruit several villain from their respective worlds, including:

Tirek
Vilgax
Mojo Jojo
Mandark
Baron Vain
Dark Danny
Queen Vexus
Dark Laser

Together they create the League of Extraordinary Villains: A group composed of several malevolent miscreants set on conquering the Multiverse. Together they then proceed to build a large army of robot and Demons to invade and concour multiple worlds!

When their evil forces begin showing up in Ponyville, Twilight and her friends just barely fight them off and discover that they're invading from another dimensions is being threatained! With no time to waist. The weilders head into the portal to stop the invading forces. Upon entering however they are seperated by another attack and end up being thrown into different portals, Twilight, Spike, Pinkie Pie, and Fluttershy are thrown into one while Rainbow Dash, Applejack, and Rarity get thrown into another. They end up fleeing through alternete worlds and meet up with several heroes from the other world's.

Twilight, Spike, Pinkie Pie, and Fluttershy encounter a stoic warrior named Jack, a kid hero known as Ben 10, the mad scientist Dexter, a fearsome trio of lab experiments called the Powet Puff Girls, and…some kids from a cul-de-sac(Ed, Edd and Eddy, who were warped there by mistake).

Rainbow Dash, Applejack, and Rarity run into a kid hero with ghost powers named Danny Phantom, a robot based off a teenage girl named XJ-9(Jenny), a boy with a power suit called Crash Nebula, a special agent known as Agent Xero, and... a little boy and his fairy godparents??

Realizing that not just their worlds, but all other worlds are in danger, it's up to all these fearless heroes to band together, defeat their archenemy's, and put an end to the League's nefarious plot of inter-dimensional conquest!