This is when Yen Sid tells everyone the legend of the Door of Destiny in G-Merl's Eternal Quest.
(Yen Sid addresses everyone in the Mysterious Tower, having summoned them there for a special purpose. King Mickey, Donald, and Goofy stand beside his chair)
Yen Sid: As a Keyblade Master, Xehanort had a gift like few others. But such great minds are often plagued by a single great question. What is the essence of the human heart that weakens us, or empowers us? The answer, he believed, would be found in the "Keyblade War." What if the challenges of our past were, in fact, a map to the light and darkness that battles within us all? Xehanort had to know, so he renounced his duties as master and chose the seeker's life. Since then, in many a guise, he has clashed with protectors of the light--Keyblade wielders like yourselves. And mark my words--he and Demigra will trouble us yet again. We must be ready. Which is why you, G-Merl are to be tested for the mark of a true Keyblade Master. No doubt you fancy yourself a master already, but it takes years of training, Only a true master can teach you the proper way. you G-Merl, are a self-taught weapon wielder--an impressive feat. However, the time has come for you to let go of preconceived notions, forget what you know about your past, and begin your training again with a clean slate.
Everyone (surprised): Huh?!
Sora: But that's a formality, right? I already proved myself. Me and the king, Riku and everyone--we can take on anything. Right, G-Merl?
G-Merl: I don't know.
(G-Merl summons his Keyblade)
G-Merl: I think that in my heart, darkness still has a hold.
(He dispels the blade)
G-Merl: Walking that path changed me. I'm not sure if I'm ready to gain my friends trust, Maybe I do need to be tested.
(Then, Tino turns back to Yen Sid)
Tino Tontini: Then count us in. Put us through the test! Just watch--me and Sunset will pass with flying colors!
(He puts his hands behind his head in a confident pose, while Mickey, Donald, and Goofy exchange glances, but then, there was a mirror against the wall)
Yoshi: What's that over there, kinda looks like an old mirror?
Princess Luna: This is no ordinary mirror. It is a gateway to another world. A gateway that opens once every thirty moons.
Pinkie Pie: Sparkly!
Princess Luna: It has always been kept in the throne room of Canterlot Castle. But when Princess Cadance took over the Crystal Empire, we sent it here for Yen Sid to watch over.
Princess Celestia: [sigh] I had always hoped that Master Xehanort would someday use it to return, to come back to Earth seeking Eraqus's guidance. Obviously, this is not what has happened.
Princess Cadance: G-Merl, you must use the mirror to go into this other world and retrieve the Chaos Emeralds, Without them, the power of Light will have no power and Earth is left without one of its most important means of defense.
Princess Luna: The Chaos Emeralds does not belong in the place Master Xehanort now calls home. And in his possession, your Chaos Emeralds will no doubt be used to bring harm to the inhabitants of this other realm. They will not have the power to defend themselves.
Princess Celestia: You understand the importance of your task?
G-Merl: Yeah, you bet I do.
Princess Celestia: Good, Then you must go at once.
Rainbow Dash: Whoa, whoa, whoa! He's going, we're going with him.
Pinkie Pie: [squee]
Rainbow Dash: Right, guy's?
Pinkie Pie: Oooh! I'm so 'nervicited'!
Applejack: You do realize that's not a real word, right?
Princess Celestia: I'm afraid I can't let you go.
Spongebob Squarepants: What?! Why not?!
Princess Celestia: Sending all of you could upset the balance of this alternate world, creating havoc that would make it impossible for G-Merl to get the emeralds back from Master Xehanort. This is something G-Merl must do alone.
G-Merl: I'm good with that.
Princess Luna: Time is of the essence. On the third day, when the moon reaches its peak in the night sky, the gateway will close. And once it does, it will be another thirty moons before you will be able to use it to return.
Everyone: [remarks of encouragement]
Yen Sid: (nodding) Very well, then. G-Merl, let your examination begin.