Unknown dimension
In an unknown universe, where there was only a gravel floor and a red storm, there was a floating robot searching for something. This was X-PO, he had a head with one eye and a floating torso with mechanical arms. He was searching until he picked up something on his scanner.
X-PO: Hey, I found the thing! Uh. I mean. "Anomaly located, master."
His master walked up to him and used his arcane abilities to lift up the object from the ground. X-PO's master was none other than Dr. Doom, who has escaped the Null Space dimension. He held in his hand a scroll with mysterious energy circulating it.
DR. DOOM: Yes… I've found it!
X-PO: Uh… you found it?
DR. DOOM: After all these months of searching, it really exists… Foundation Prime. This depicts the Foundation Elements - artefacts from the start of time, scattered across the dimensions. And only I can gather them all in one place.
X-PO: Just so you know… the Foundation Elements are the cornerstones of time and space. So they're… Kinda important. To the… Entire Multiverse.
DR. DOOM: Your services are no longer required.
Doom then opens a portal using his arcane magic.
X-PO: But the elements can't be safely harnessed - it's too dangerous!
Doom then kicks the robot into the portal.
X-PO: And what about that pay raise you promised meeeee…?!
The portal closes and Doom looks at the scroll.
DR. DOOM: Mhmhmhm, with these Foundation Elements, I will have my revenge against those who defied me! I will have them all. I will control their power. I will make universes collide!
Suddenly, Doom's body glows a blood red aura and starts flickering out of reality. After a few seconds he gains control.
DR. DOOM: No! I will not be denied perfection! My dedication to this work has taken its toll. Not for much longer can I freely pass between dimensions… But, there is another way. Ha Ha Ha Ha Ha.
Earth Prime (Avengers Compound)
Sonic The Hedgehog, who had the final Chaos Emerald in hand, was running toward the Avengers Compound to inform his allies. He reached the entrance.
SONIC: Guys! I've got it! The final Emerald!
DR. EGGMAN: Hohohohohoho!
Suddenly, Dr. Eggman descended down to Sonic in his Egg Mobile.
DR. EGGMAN: This time, I'm one step ahead!
SONIC: Eggman!
DR. EGGMAN: A perfect addition to my collection!
He shows off 6 of the 7 Chaos Emeralds.
SONIC: What makes you think you can poach it from me?
DR. EGGMAN: Hmm... Decide if your friends are worth saving.
As he said that, an army of Badniks bring out Tony Stark and Tails.
DR. EGGMAN: Or if you wanna stop me from using this Keystone Device.
On the front of his Egg Mobile is a device that resembles a claw but it is actually a portal gun.
DR. EGGMAN: Once I controlled Time using the Emeralds alone... Now I have the Device, their combined power will allow me to control the Dimensions for generations to come!
COMPUTER: System charging, Focusing Device.
SONIC: If only your plan was as flawless as your mustache, Egghead!
He dashes off.
DR. EGGMAN: Why, thank you, Sonic! You know, I think after 25 years of being-arch-enemies we've really grown a soft-spot for one another and... HEY!
While he was distracted, Sonic had set his friends free.
SONIC: I think that plan's scrambled! See what I did there?
DR. EGGMAN: Whaaat?
SONIC: I released Tony, who saved Tails, in which we all trashed your Badniks.
DR. EGGMAN: Grr, this changes nothing. Dr. Eggman will still have the last laugh!
He was about to attack but then suddenly a Batarang struck the Egg Mobile. They all looked up to see Batman on top of the Compound.
DR. EGGMAN: Wh-What, you?
Batman then jumped down and landed next to the heroes.
IRON MAN: Well this was unexpected.
SONIC: What are you doing here?
BATMAN: I picked up a dimensional anomaly, and i'm guessing it's from that device.
Suddenly the device begins to shake.
COMPUTER: System overpowering. Device unstable. Dimension breach.
The device then opens a rift and the Emeralds get sucked in, while Eggman is about to follow suit.
DR. EGGMAN: Wooooah! Not again!
He gets sucked in.
SONIC: The Emeralds!
Sonic rushes in after them.
IRON MAN: SONIC NO!
Iron Man and Batman rush in after him. The portal closes while Tails is left wondering what had just occurred.
The Lord of the Rings universe
Gandalf the grey was facing against the Balrog on a bridge.
GANDALF: You shall not pass!
He hits the bridge with his staff which causes it to collapse, sending him and the Balrog down the pit.
FRODO: Gandalf!
GANDALF: Fly you, fools.
FRODO: Nooo!
As the two are sent down the pit, a rift opens up and the three heroes emerge from it.
SONIC: Where are the Emeralds?
GANDALF: What? Behind you!
The tail of the Balrog almost hit the heroes but they dodged it just in time.
IRON MAN: He said, where are the Emeralds?
GANDALF: My dear fellow, I have no idea what you are talking about. Have you tried looking in a tree?
BATMAN: What? Look they got sucked into a weird hole in New Metro. We jumped in and it led us to you!
GANDALF: And you are?
SONIC: Sonic, Sonic The Hedgehog.
IRON MAN: I am Iron Man.
BATMAN: I'm Batman.
Iron Man then fired his unibeam at the Balrog and it fell further, while Batman grabbed Gandalf and used his grappling hook to get them to safety, while Sonic just ran and jumped up the walls.
GANDALF: My thanks.
FRODO: Gandalf!
Suddenly a rift opened up and sucked him in.
GANDALF: Frodo! The Ring! Frodo has the One Ring - it cannot fall into the enemy's hands! Quickly, fly!
BATMAN: I'm not an actual bat, Gandalf!
The three heroes then entered the rift.
New York City (Earth 2003)
As the Teenage Mutant Ninja Turtlesand Master Splinter fight the Purple Dragons, a rift opens up between them. Hun is confused but is then spin dashed into a stash of wooden boxes. The turles look to see the four heroes emerge from the portal.
RAPH: What the shell?
BATMAN: Ninja...Turtles?
DONNIE: Uhh, who are you guys?
IRON MAN: That was gonna be our question.
GANDALF: It doesn't appear that the one ring or Frodo is here.
MICKEY: Uh, who?
MASTER SPLINTER: My sons, I believe….
He is then cut off when a rift opens up and he is pulled through.
TMNT: MASTER SPLINTER!
Sonic then rushes in to save him and the other 4 heroes follow with Leonardo in hot pursuit. His brothers try to follow but the rift closes.
MICKEY: Dudes, what do we do now?