DC Universe, Gotham City...

It was yet another night, the peace interrupted by the sound of multiple high-speeding vehicles passing in the street. Ahead was a small car, inside was a large man with a giant tank strapped to his body, a green rock in his hand. "Finally. I can do the impossible... If I cannot break the Batman, I will break the Superman instead!"

Behind him in the chase was a familiar black car and a red motorcycle. "What do you think Bane would want Kryptonite for, Bats?" asked Robin with genuine curiosity as he focused in front while rising his motorcycle, his hands on his handles, seeing that their enemy had never resorted to stealing such an item.

Inside the Batmobile was Batman, who pressed a few buttons, "Why else, Robin? He wants to defeat Superman. Unfortunately for him, we're on his trail. On my signal, I want you to go ahead while I initialize the Batmobile's targeting system to blow out his tires to stop him." he ordered, getting a response from his partner.

"Alright!"

Robin revved his bike and rode ahead of Batman, the Dark Knight ready to attack Bane. The Boy Wonder knocked on the window, "Hey, Bane! Open up, it's time you got what you paid for!" he quipped, his voice muffled from the other side.

"I will not listen to you boy!" Bane shouted.

The car Bane was driving began to swerve, prompting Robin to move, but he noticed that it was not an action to stop him, "Uh, Batman... Did you hit his tires already?"

From the Batmobile, Batman answered, "No... I'm detecting a high energy spike coming from nearby. Be on the lookout, Robin." he warned Robin, who tried to control his motorcycle.

Then, suddenly, next to Robin, the wall broke apart, revealing a blue vortex in the alleyway, it pulling in Bane. Robin newrly flew in and used his grappling hook to hold on to something. "Ah!" he screamed, holding on as much as he could.

"Robin!" screamed Batman.

He hopped out of the Batmobile, but the pull of the mysterious portal got Robin and he fell in before the Dark Knight could save him, with Batman chasing after him. He didn't know where the portal was going, but he had to save him.

Marvel Universe, New York City...

"Wow, really? The whole 'I'm going to destroy you, Spider-Man' act again, Goblin? I expected better from you." quipped Spider-Man, webbing onto the Green Goblin's glider. The wall-crawler was flung around, hitting the side of a building.

Goblin sneered, "For once, why won't you just quit?"

Spider-Man perched himself on the wall, hopping off and kicking Osbron in the face, "Because quitting isn't in my vocabulary, Gobby! We've done this dance before!" he said, seeing the Green Goblin get his bearings upon landing on a rooftop.

Coughing, Osborn gritted his teeth, "How...? I've torn apart your life so many times, and yet you keep coming back... This time, I'll kill you... And that's it."

Shrugging, Spider-Man webbed up Osborn's arms, tying them down. "Okay. Come on out."

"Who-?"

A set of claws slashed Goblin in the face, creating small scratch marks on his green masked face. A woman wearing a black latex suit and a domino mask smirked, hopping next to Spider-Man. "Knew you couldn't resist, Spider..."

"...Right. Thanks for lending a hand." he replied, 'MJ's gonna kill me if she hears about this.'

Black Cat nodded, "It was no problem. Seems Goblin here can't seem to learn."

The crime-fighting duo heard Goblin laugh. Spider-Man clenched his fists tight, "What's so funny, Osborn?" he asked, "We already stopped you. In record time, too."

A smirk was seen on Goblin's face, "Because I didn't come alone..." he growled.

A familiar tingling sensation rang in the back of Spider-Man's head. "Everything ok, Spider?" asked Black Cat with concern. "He's probably bluffing anyway."

Instead of speaking, Spider-Man grabbed Black Cat by the arm and pulled her away from the attack, which was caused by an unknown source. In those few seconds, Green Goblin freed himself from the gossamer on his arms and shoved the two heroes off the roof. Peter yelled, decking Osborn in the face.

"Are you crazy, Osborn? You'll kill us!" Spider-Man said.

"Yeah, I didn't think you were this crazy!" Black Cat huffed.

"Oh, there's more to this than you think..." cackled Goblin.

Spider-Man flipped himself so that he was able to stomp on Green Goblin, but Black Cat was still trying to fight him from her spot in midair. Below, Peter noticed a swirling blue rift. "Cat!" he yelled, seeing the villain and ally fall in there without a trace.

"Spider!" she said before falling in with Goblin behind her. Spider-Man was ready to chase after her, but something grabbed him before he could dive in.

'What the-?' he thought, feeling someone grab his leg. He faced upward, seeing someone clad in black and gray wearing a pointy-ear cowl and holding onto a grapnel gun. "Uh... Who the heck are you?" he questioned the stranger.

"I'm Batman. And we need to talk."

Pausing, Spider-Man nodded, "...Okay... But can we do this after we jump in the mysterious portal? I have a friend that needs help. Maybe."

"That's it. I just came from one. I saw that Goblin person fall in there. It seemed intentional. One of my enemies did the same and took my partner, Robin as well." Batman revealed.

"...So you're a hero from another dimension that is dealing with the same problem as me?" Spider-Man asked with a sigh, "With how crazy my life's been, why not? I'm Spider-Man, by the way, and from the sound of it, we have a common enemy. So, how about we head in there and see where the rabbit hole takes us?"

Nodding, Batman agreed, "Very well."

And so, the duo jumped into the portal, heading into unknown territory once again.

Sonic's World, Green Hill...

Sonic the Hedgehog and Tails the Fox ran after their nemesis, Doctor Eggman, who had a familiar glowing blue gem in his hand. "You can't lose us, Egghead!"

Slamming his fist on the rim of the Egg-Mobile, Eggman hissed, "You of all people should know, my name is Eggman! You do that on purpose!" he yelled.

"Do what, Egghead?" Sonic asked. The hedgehog looked to his two-tailed friend, "Hey, buddy. I think we've done enough toying around. It's about time we got the first emerald."

Tails nodded, "Right!" he spun his namesakes around, giving him the ability of flight and went ahead of Sonic, "Hey, Eggman!" he greeted, a devious smirk on his face, he snatched the Chaos Emerald right out of the scientist's grip. "I got it!"

Sonic gave his friend a thumbs up, "Alright, bro!"

"Give that back!" Eggman yelled.

"Gotta catch us, first, Eggman!" Sonic yelled, finding himself ahead of Eggman's hovercraft.

Said doctor tried to fly after Tails, but the fox found himself in the gravitational pull of something. He tried to swim in midair, "Ugh..." he groaned, seeing a blue portal behind him. He heard Eggman scream, getting pushed in as well.

"Tails!" Sonic yelled, trying to jump as high as he could.

"Aahhh!" Eggman and Tails yelled, flying into the portal after pushing one another accidentally.

"Sonic!" the hedgehog could hear, before Tails flew into the portal, it closing behind the geniuses.

Sonic raised a hand, closing his eyes, "Tails..." he opened his eyelids, "I gotta find whoever did that... And fast."

He was about to run, but he heard the sound of popping. He turned around and saw two humans jump out, both of them wearing strange costumes. Sonic quipped, "Did I miss some kind of Halloween party or something?"

"Says the Looney Tunes reject." Spider-Man quipped back.

"What did you do to Tails?" Sonic snarled, ready to hit the duo with a Spin-Dash.

Batman extended a hand, "We have nothing to do with whatever happened. I'm Batman, and that's Spider-Man. Tell me, did a portal show up and grab a friend of yours?" at the hedgehog's nod, he continued, "The same happened to us."

"Yeah. We're on your side." Spider-Man explained. "Honest."

Sonic crossed his arms and sighed, "Hm... Alright. But if this is a trap, then I'm gonna make ya eat my dust and the floor." he warned the superheroes. "Name's Sonic. Sonic the Hedgehog."

Batman and Spider-Man faced the portal with the newcomer, "Alright, Sonic. Let's go." said Spider-Man. The new team hopped into the blue vortex, wondering where they were going to end up next.

Unknown...

The three landed on the floor. The room they were in was dark, and they could see crystals. "It looks like we're in some kind of cave." deduced Batman.

"Looks like it." said Spider-Man, dusting his costume off. "Now where are we?"

Sonic looked around, "I... Have no clue."

"Someone is doing this intentionally." realized Batman, "Our worlds. Our allies getting captured as well as an enemy. I have no idea as to what this place is, but we're here for a reason. And I'm going to get to the bottom of it."

Raising a finger, Sonic corrected, "Uh, we're getting to the bottom of this. This is our battle as much as it is yours, Bats. Now, if only we had a clue as to who's doing this."

The three turned their heads, spotting a strange gateway, "Well, I think we have one clue." joked Spider-Man, he knelt down, grabbing a handheld of sorts. "...And this looks like it could come in handy."

A blue glow suddenly appeared in the gateway, causing the trio to hop back in surprise. They eased once they saw it was yet another portal. "Huh. That's strange. How did it turn on?" Sonic wondered.

Spider-Man looked at the scanner, "I dunno. But I'm getting a strange reading on this thing. I think it might be a detector or energy scanner. We should probably keep this handy."

"We should." agreed Batman, "But the three of us aren't getting answers by standing here. We have to find out who or what is doing this." he reminded the three in a stern tone.

"Yeah, let's go!" Sonic smirked.

Spider-Man rolled his eyes, "Are you always this excited?"

Sonic shrugged, "Hey, I like a good adventure every now and then. And this time we got friends to save, so we gotta hurry."

"Then let's go." ordered Batman.