A Monster in Canterlot/Transcript

Opening
Theme song)

(A title card “Guest staring: The Mane 6”)

Shaggy (voice): Today we meet Twilight and her friends.

New Royale City is dominated
(The Mystery Inc sees New Royale City's been dominated and deserted, everyone are missing after Lorcan's funeral)

Daphne: What happened here?

Velma: I don't know. It's probably been... destroyed.

Fred: I don't get it, first this place is amazing and now it's in destruction, i mean we're here to visit, Cillian and Lilly.

The Execution Demon appeared
Rainbow Dash: Hello?! Is anypony or anyone in the barrel?

Shaggy: Nobody in here, but us chickens.

Fluttershy: That's right. Oh, this is why i missed Lorcan.

Rainbow Dash: Same here.

Shaggy: Wait, you know Lorcan?

Rainbow Dash: Know him? Lorcan's our good friend. He has a funny-side, love adventures and sometimes we both beat each-other up to make everyone laugh.

Velma discovers the girl's soul
(Velma hears something and walked into a room)

Twilight Sparkle: Uh, Velma, i wouldn't go in there if i were you.

Velma: Why?

Spike: Why not, Twilight?

Twilight Sparkle: That room where all the souls are.

Velma: Let's see them.

(Velma opens the door. All of the souls are missing, All except one)

Shaggy: They're gone. They really are.

Fluttershy: Oh my. Look.

A Girl:  I don’t recognize you. You are new. I remember this... scenario however. It’s a strange thing to want to do, to come here. I’m curious what events would lead a person to want to spend their nights in a place like this... willingly. Maybe curiosity, maybe ignorance... There is a space under my room. I recommend that you hurry though. You will be safe there, just try not to make eye contact... it will be over soon. Celestia will lose interest.

Twilight Sparkle: She's right. Hide!

(Velma, Shaggy, Scooby, Twilight and Fluttershy hides from Celestia until the coast is clear)

A Girl:  When your dragon comes back, he is going to tell you that he was unsuccessful, that you must free me. Can you help me?

Twilight Sparkle: Don't worry. I will help.

A Girl: Good, Spike will then tell you to go back to New Royale City. If you follow my instructions, i will die. Your friend, Lorcan will not be able to coming back in this dimension anymore. He will miss you, Mystery Inc. The power will be restored shortly. When you return to the city, go rescue Daphne and Fred. Celestia and the Execution Demon cannot see you and can only listen for our conversation. When you hear my music become louder, i will warn you to freeze, listening for you. Wait, and be still.

(The girl disappears)

Shaggy: Wait... Lorcan is still alive?

Twilight Sparkle: You didn't know? He's gone home to his dimension to be with his family.

Fluttershy: Yeah, he was dying but once when we found Lorcan in the forest, we helped him get home.

Velma: We better tell the others.

Twilight Sparkle: Right there's no time to lose.

(They head back until The Execution Demon appears)

Shaggy: Zoinks! Like run!

(Shaggy, Scooby, and Fluttershy run the other way as the demons chases them)

Shaggy: Faster, faster! Like, he's gaining on us!

(They continue running)

Celestia shows her true colors
Voice: There you are!

(It was Princess Celestia)

Velma: Princess Celestia, boy are we glad to see you.

Princess Celestia: Yes, but for the last time! (She blasts them)

Shaggy: Zoinks! What's with you, pony princess?!

Twilight Sparkle: No... she was... evil? (sees Princess Celestia eyes) No! she's under a spell!

Daphne: By who?

The Execution Demon: (offscreen) By me!

(Then, he jumps to the gang)

Celestia and The Execution Demon chases the gang
(Shaggy, Scooby, and Fluttershy runs when Princess Celestia is chasing them)

Shaggy: Zoinks! She's gaining on us!

Cillian and Lilly to the rescue
(The Mystery Inc are in the dead end with the Mane 6 while Celestia and the Execution Demon got them)

Princess Celestia:  This is where it ends. Surrender now.

Shaggy: Hohoho! Like, I'm too young to be executed!

The Execution Demon: Prepare to meet your doom!

(Just then, Cillian and Lilly appeared in between of the Mystery Inc, Mane 6 and Celestia)

Cillian: Shaggy, Scooby! Don't worry!

Princess Celestia: You again! You will be executed!

Lilly: It's over, Celestia and there's nothing you can do to stop us!

Princess Celestia: Get them!

(The Guards start fighting Cillian and Lilly)

Twilight unmasked The Execution Demon
(The Execution Demon is caught and Twilight unmasked him)

Twilight Sparkle and Lilly: Prince Blueblood?

Cillian: The first Guardian of the Gate in Lorcan Darcy's Adventures Season One?

Prince Blueblood: That's right!

Rarity: But why?!

Prince Blueblood: I wanted to keep Lorcan's past a secret! Sure he maybe Cillian but he is not dead!

Daphne: What? But if he's not dead... wait that rocket... is it true, Cillian? Lorcan was in that rocket?

Cillian: It's true. He had enough traveling here. So while you guys are here for a visit, we both came up with a plan to escape from the city and go into the forest for two weeks.

Lilly: And then we all found him at the cave and then, we discovers that he's dying in pain, all of our friends who we met came to us to say our goodbyes to Lorcan before we send him home.

Shaggy: I never know that. But, what happened to Princess Celestia when the demon shows up?

Fred: Prince Blueblood put Celestia under a spell so she could be alongside the Execution Demon to scare everyone away.

Cillian: Except for Lorcan, we all know that. But when Lorcan uses his powers to fuse dimensions, we're gonna help him to defeat you Celestia once and for all and also we are gonna free the Girl's Soul.

Twilight Sparkle: Wait. You're really are that evil? Cillian, it's time to tell everyone what's the girl's soul's name.

Princess Celestia: Don't you dare!

Cillian: The girl's soul's name is... LORCAN DARCY!

(Everyone shocked that Lorcan was that girl who was kidnapped by celestia)

Ending
TBA