Back in the other world, Knuckles, Ruby, and everyone else show up at the address which General Ironwood mentioned.
Ironwood: Everyone's here. Let's go over the plan. We need someone fast enough to sneak into the generator room and shut down the defense systems so that we can launch our attack.
Ruby: If you want someone fast, I'm your girl.
Mighty: Well, she's the only fast person we got here right now so yeah.
Ironwood: Precisely. And that's going to be our advantage.
Vector: She's not Sonic but she'll do.
Ruby: Heh heh.
Yang: Kay sis. You just go on and do what Sonic would do.
Ruby: Roger that.
While they discuss things, Vector looks at Ironwood with a straight face as he begins to remember something about him. Something very serious that...
Vector: WAIT A MINUTE!
Everybody looks at Vector.
Knuckles: What's wrong?
The crocodile points at the general.
Vector: He should be in jail for life!
Ray: General Ironwood?
Amy: Why? What did he do wrong?
Vector: It said on the news that he committed treason in Mantle a few years ago and was sentenced to life in prison!
Mighty: Treason?
Espio: Is this true, General Ironwood?
Ironwood: He's... not wrong.
Weiss: Listen, Vector. It's kind of a long story.
Vector: Why is he even here?! How is he not in jail right now?
Glynda: Calm down, Vector.
Robyn: You may not know this, but Ironwood was given a pardon just recently.
Ironwood: I take full responsibility for all that's happened back there. I know I can't be forgiven, and there are lots of things I have to do to redeem myself. That includes helping with the reconstruction of Mantle.
The crocodile walks out, saying nothing.
Mighty: Vector?
No response. Mighty, Ray, Knuckles, Espio, Charmy, and Amy go after him. They see their friend sitting down on a log by the lake.
Knuckles: Hey Vector, come on.
Amy: I know it's a lot to take in. But we need his help.
Vector: I don't trust that guy one bit. Because he's more than just a criminal.
Mighty: If you don't trust him, then trust us.
Vector: Alright, fine. I trust you guys because you're my friends.
Espio: Good. We don't have time to worry about treason right now. We have friends to save, and an island to take back.
Vector: Right. Let's get this over with so I can go play Rocket League.
Ray: We should pay a visit to the Underworld as well, and see how Ronie, Tiese, Sortiliena, and everyone else are doing since the war is over.
Mighty: Good idea. Add it to the list of plans.
Meanwhile, in the other dimension, Tails and Tatsuya finally finish building the dimensionator.
Tails: Okay, just one last component.
He turns a screw in, and success.
Tails: Okay folks! Done and done!
Tatsuya: Let's make sure this works.
They turn it on and a portal opens.
Tails: Dimensional Rift stabilized! Perfect!
Everybody else arrives, seeing how the project is complete.
Sonic: Alright! Nicely done!
Tails: It should be able to get us back to our world.
Sonic: Way to go, you guys!
Mizuki: I guess this is goodbye, huh.
Erika: Man. I really had fun hanging out with you guys. I'm really gonna miss you.
Tails: Hey, uh. We can see each other any time we want. We have the dimensionator right here.
Tatsuya: You're right.
Miyuki: Good luck, Sonic. Tails. Win for us, okay?
Sonic: You got it.
Honoka: Take care, you guys!
Leo: Good luck.
Mikihiko: Be safe out there.
Mayumi: We'll be right here if you need us.
Mari: Come back soon, okay?
Miyuki: We'll see you soon.
Tatsuya: When you come back, chili dogs will be on us.
Sonic: Wow! Thanks! Come on Tails. Let's go home.
Tails: Yeah.
The duo jumps inside the portal as everyone waves goodbye. It closes.
Tatsuya: Good luck, Sonic.
Back in Sonic's world, the team arrives near Robotnik's base.
Charmy: How many military factories does this guy have?
Vector: More importantly, how's he able to afford all of them?
Mighty: Well, he wouldn't need so many if we weren't always trashing them.
Ironwood: Okay, Ruby. Are you in position?
At the outer wall, by an air duct...
Ruby: Red hawk, going in.
She uses her semblance to speed into the air vent, making her way into the generator room. Once she arrives, she finds the fuse box and opens it up.
Ruby: Okay. I'm here. Now, uh... Man, these aren't even labeled. You know what?
She takes out Crescent Rose and shoots the fuse box, destroying it.
Ruby: Okay. That should do.
The lights go out, and power all around the base goes down.
Dr. Robotnik: What the... Who turned out the lights?
Cinder: We seemed to have lost power.
Back outside...
Ironwood: O-kay? I guess that'll do. Everyone! Move in!
Mighty: Let's rock and roll!
Everybody rushes into Eggman's base.
Vector: This might actually work out okay!
Announcement: Backup power activated.
The power goes back online.
Charmy: Well that's not good.
Vector: So much for no power.
Pyrrha: Don't worry. We got this.
Knuckles: Weiss? Yang? Blake? Go find Ruby.
Weiss, Blake, and Yang: Right!
Mighty: Let's pay Eggman and Cinder a visit.
Everybody breaks into Robotnik's office, to confront both him and Cinder.
Knuckles: Alright Eggman! Give us back our friends!
Dr. Robotnik: Ah. You're back. And you've brought some new friends as well.
Cinder: Those students from Beacon, Haven, and Atlas along with the teachers. And is that Ironwood?
Ironwood: Surprise.
Meanwhile, with Team RWBY...
Yang: Ruby! There you are!
Ruby: Okay, was auxiliary power part of the plan?
Blake: Probably not. Either way, Robotnik's screwed.
Weiss: Let's hurry to the others.
They get surrounded by a swarm of Egg Robos and Buzz Bombers.
Weiss: But first thing's first.
Ruby: Heh heh.
Yang: What is it?
Ruby: It's been a while since it was just the four of us, don't you think?
Yang: Oh yeah, it has.
Blake: I'm kind of getting nostalgic.
Weiss: Same here. A lot's happened over the years. Let's all fight together.
Team RWBY: Yeah!
Ruby: Okay badniks! Make way for Team RWBY!
Yang: A.K.A, the Beacon Grad Girls!
Back with the others...
Dr. Robotnik: I think it's time we took out the trash. Team Metal! Go!
A door on the floor opens up, and a trio of adversaries created by Robotnik appears. Metal Sonic, Tails Doll, and Metal Knuckles.
Ray: Well, we haven't seen Tails Doll or Metal Knuckles in a long time.
Nora: I do not like the look of that doll.
Jaune: That's creepy.
Coco: You really think those three are gonna beat all of us?
About three Death Egg Robots appear, along with the Hard-Boiled Heavies.
Coco: Should have kept my mouth shut.
Mighty: How's it going, Heavies?
Dr. Robotnik: Now we can let the fight begin! Team Metal, Death Egg Robots, and Hard-Boiled Heavies! Attack!
Just as the robots prepare to fight, a portal opens up on the right, and a blue blur of light shoots out, destroying the Death Egg Robots.
Vector: What the...
?: Oh jeez!
A blue guy wearing shoes and a hoodie is stuck in the wall. He pulls himself out.
Sonic: Why the heck does this keep happening?
Knuckles, Mighty, Ray, and Amy: SONIC!
Sonic: Well this is quite the crowd.
The two-tailed fox comes out of the portal and flies down.
Tails: Hey everyone!
Mighty: Tails! You guys are back!
Vector: Man! It's about time!
Ray: Nice hoodie, Sonic.
Sonic: Thanks.
Dr. Robotnik: Welcome back, hedgehog! Certainly took you long enough, eh?
Sonic: It's only been a few days but yeah. Anyway, let's finish this, Eggman!
Dr. Robotnik: Heavies! Team Metal! Attack!
Metal Sonic charges at his foe.
Sonic: This is a lot of my worst foes.
Dr. Robotnik: You gonna go in too, Cinder?
Cinder: No thanks. I'm already finding this entertaining. Seeing that blue boy in action.
Coco: Okay. Here goes.
Coco's handbag transforms into a gatling gun, and she shoots at the Heavies.
Mighty: Holy snap! That purse is a gatling gun?!
Sonic: That gatling gun's a purse?!
Coco: This is Gianduja. Cool, eh?
Sonic: Wow.
Vector: Where do you guys get this stuff from?!
Ren: Long story.
Vector: Man. They got all these cool weapons and fancy super powers.
Pyrrha: What's wrong? Jealous?
Vector: Oh shut up.
Sonic and his metal self continue the fight. Each going at each other with full speed using homing attacks and spin dashes, and Sonic having to dodge Metal Sonic's laser beams coming from his belly.
Pyrrha: This probably wouldn't be fair, but...
Pyrrha uses his semblance on all the robots. slamming them to the walls, ceiling, and finally, down on the floor. Takedown.
Sonic: Gee, thanks Magneto.
Pyrrha: Hee hee.
Qrow: Maybe we didn't have to come down after all.
Dr. Robotnik: You may have taken down the bots, but there's still a powerful doll right here.
Tails Doll begins to grow a gigantic ball of electricity over its head.
Sonic: Giant electroball. No prob...
Suddenly, the giant ball just disappears.
Dr. Robotnik: What?!
And the doll gets frozen in a block of ice.
Espio: What was that?
Ren: That wasn't any of us, was it?
?: We assumed you needed a hand.
Tatsuya, Miyuki, and their friends come out of a portal, greeting everyone.
Sonic: Tatsuya?!
Tails: You guys came?!
Erika: You were fighting an evil scientist and we thought, "hey let's join in."
Knuckles: Who are they?
Sonic: They're our friends from the other dimension. They helped us get back home.
Mighty: Awesome!
Dr. Robotnik: Grrr! Curse you blasted anime people!
Miyuki: So that's Dr. Robotnik?
Sonic: The bald guy with the mustache? Yep. That's him.
Dr. Robotnik: I've had it up to here with you! Time to get rid of you all once and for all!
Robotnik sends out a massive swarm of badniks and Death Egg Robots. Tatsuya readies his CAD, aims it forward, and all the robots disappear, leaving critters coming out.
Dr. Robotnik: What the heck was that?!
Tails: What kind of magic ability did you just use? They just disappeared.
Tatsuya: Demon Light.
Tails: Demon Light?
Tatsuya: It was created a few years ago in Okinawa. It lets the users targets dissipate like mist.
Sonic: Okay that's really insane.
Cinder: This might be fatal if we continue on. We should leave.
Dr. Robotnik: You go on first. I'll stay here and take out my special weapon.
Cinder: Okay.
Cinder takes her leave, while Eggman calls in an Egg Dragoon.
Dr. Robotnik: Let's see how many seconds you last against...
The Egg Dragoon disappears, and the mad scientist with his Egg Mobile falls down on the floor.
Dr. Robotnik: *Sigh*
Tatsuya: It's over, Dr. Robotnik. You lost.
Dr. Robotnik: Oh yeah?! I guess I'll just destroy you all myself!
Robotnik takes out a blaster.
Sonic: Hey Eggman!
Dr. Robotnik: What?!
Sonic: The exit is that way.
Robotnik looks around and gives a sigh. He walks on back to his Egg Mobile and turns the key, starting it.
Dr. Robotnik: See you tomorrow, Sonic.
Sonic: Oh, wait. One more thing.
Sonic grabs a piece of metal and throws it at the Egg Mobile, making it explode, sending Eggman flying up through the ceiling and into the sky.
Dr. Robotnik: I HATE THAT HEDGEHOOOOOOOOG!
Ding.
Sonic: Well, the fight's over.
Tails: Finally. Thanks for the help, guys.
Miyuki: No, we should thank you. Because of you both, we stopped a terrorist attack from happening in our world. We owe you a lot.
Erika: Next time you fight an egg, let us know. We'll be waiting.
Sonic: Hey the eggs are my gig.
Jaune: I guess we can all relax for now.
Vector: Yeah. It's summer and I wanna go play Rocket League until the next story.
Team RWBY arrives.
Ruby: Hey guys! Sorry we're la... Oh. Did we miss something?
Velvet: The whole fight.
Yang: Oh. Well that stinks. Looking good, Sonic!
Sonic: Thanks.
Tatsuya: We should probably head out of here before the base explodes.
Qrow: Good idea.
Knuckles: How many more anime people are there?
Sonic: Save it for E3.
Everybody starts walking out.
Knuckles: What's E3?
The base starts exploding.
Knuckles: Gah! Okay time to go!
Shortly after everybody heads out, the entire base explodes. At last, they finally took back South Island.