This is how
They are falling into Darkness
Gaomon: I guess it's the end of us.
Lann: Mom... Dad...
Vivi: Now we can be... one of Darkness...
Then someone save them it was Fuyunyan, Mickey, Bugs, Optimus, Zig and Bumblebee
Fuyunyan: We got them.
Bugs: Who are those guys, Doc?
Mickey: Let's get them to safety.
They take them to safety
Zig: Are you ok?
Gaomon: We're fine, but who are you?
Optimus: There's no time to explain.
They saw Heartless
Gaomon: The dwellers of darkness?
Fuyunyan: They called Heartless!
Zig: Let's get those Heartless!
They are fighting them when they defeated them
Mickey: Better not push our luck. Gosh, we never the we found you and your friends in the realm of darkness.
Bugs: Yeah. [takes a bite of a carrot] I hope you lot are ok.
Gaomon: Have you seen our Partners?
Lann: Our Parents.
Vivi: Zidane and Dagger?
Mordecai: And Pops?
Fuyunyan: No, just you and your friends.
Optimus Prime: My name is Optimus Prime. Me and Bumblebee are atomonus robotic organisms from the planet Cybertron.
Zig: Or you can call them Autobots for short.
Zig: Yes, chap. I am Zig the hyena. I got here when my and Sharko's world fell into darkness.
Fuyunyan: Name's Fuyunyan.
Bugs: I'm Bugs Bunny.
Mickey: My names Mickey.
Vivi: Great to meet you. I'm Vivi, this is Lann, Raynn, Gaomon, Agumon, Lalamon, Falcomon, Mordecai and Rigby.
Agumon: And we're sorry. The Darkness in this place it's getting to us.
Mickey: Oh. but, you'll be okay.
Fuyunyan: Say. How come you're in this place?
Vivi: We got knocked out from a Digimon. But for Lann and Raynn they left Grymoire and ended up here.
Mickey: I... didn't know.
Raynn: How about you? What could've brought you here? Has something happened? In the Realm of Light.
Bugs: It's the Heartless. They've been attacking worlds and taking their hearts. And world's with no hearts vanish into Darkness. But if we can lock the door between the two realms- light and dark- from both sides, we can protect the other worlds. And you know, we came here to find those items on this side. Turns out, it's not so easy getting into the realm of Darkness. The point you can cross have been unstable. It's only when a world gets consumed, that an entrance appears in the realm between. So, waited my chance... To sneak in. But hey, when we got here. We felt warm, familiar lights. We follow it to find our way to you and your friends.
They pointed their hearts
Raynn: Our Hearts.
Lalamon: So they were helping, our friends have brought you and us back together.
Fuyunyan: Of course.
Mordecai: But, the world's are still in danger?
Rigby: Say, did our world's is still okay?
Mickey: I don't think so.
Gaomon: Okay, but what every happens to everyone, they'll be okay. They'll find their way home. I just know it.
Bugs: I think you're right, they'll be okay.
Lann: We have to go and head back to the realm of light.
Zig: Great then, let's go locate those items and go home together.
Agumon: So you found a Way out?
Fuyunyan: Well... Oh.. we were so busy finding the way in, that we didn't give a lot of thought to where there'd be a way out. But, together we're sure to find one!
Bugs: May our hearts be our guiding key.
Gaomon: What was that?
Mickey: Keyblade, Digidestined, Digimon and Warrior Wielders used to say those words to each other. And now, it's something we like to try and remember. So, ready?