Here's how Brian's accident, Thomas gets in charge, and discovering the Nightmare Family and Chrysalis' existence goes in Revenge of the Nightmare Family & Changling Queen.
(the next day, everyone is working on the new Gala)
Brian: (wearing a hardhat and whistle, while holding a clipboard) Okay, everyone. We've only got a week to get this Gala complete, so let's not dilly-dally! Now, any questions?
Construction worker pegasus: Yeah, can we have a real general?
Brian: I have no time for questions! Now all of you get to work!
[then Blythe and Rarity bring in several fabrics]
Rarity: Man, Brian's killing me.
Blythe Baxter: Well, we only have a week to get this Gala together. Brian's probably got a lot on his shoulders. I mean how do you think you would feel if you had only a week to fill a big order of dresses for an important client?
Rarity: Hmm. I can see your point. But Brian better take it easy, he might have an accident.
Brian: I heard that!
Rarity: Well excuse me for at least showing concern for you!
Brian: Just get those fabrics ready for the decor! Time is on the essence here! I'm gonna go and get more of the merrier!
[Brian then leaves the room to get more supplies]
Zoe Trent: I hope he doesn't over do himself.
[Brian is now carrying a giant box of banners and ribbons]
Brian: Huh, I'm actually getting the hang of this. There is nothing than can break me right now.
[but then when he reaches a set of stairs, he accidently slips on a rug!]
Brian: Whoa! [tumbles down the stairs yelling and grunting as the box spills all its contents] Oh, no. [he tries to get up, but he couldn't stand. His ankle was broken!] OW!! Oh, my God!
Vinny: Oh, are you okay?
Brian: I JUST FELL DOWN SOME, FLIPPING STAIRS! DON'T TOUCH IT!
Vinny: Can you try to get up?
Brian: No, I need your help.
Vinny: Alright. Just give me your arm.
Brian: Okay. [grabs Vinny's hand]
[Vinny then lifts Brian up as Brian groans in pain]
Vinny: Don't worry, we'll take you to the hospital.
Brian: But who will get the Gala ready on time?
Pricness Celestia: Thomas will hadle that. Because you had been careless to be a good leader.
Brian: You saying I'm bad?
Barret Barricade: Yes, Brian. A leader shouldn't yell at it's workers. It's not like being a general!
Brian: Well, Thomas didn't save Blythe, I did!
Vinny: Alright, knock it off, or I'll break your other leg.
Brian: Who says?
Vinny: I says, if you don't like it, you can hop to the hospital while I walk!
Brian: Okay, okay!
Vinny: And don't worry, when you're back from the hospital, you'll be back in charge again. But you have to admit, you were being a bit too bossy.
Brian: Hmm. You're right. When I return, I should try to be a bit more easy.
[However, Brian saw Thomas chuffing by inside and everyone cheers saying: "Hooray, Thomas is here!". And that made Brian cross, infact he was holding his right fist]
Brian: [to himself] Thomas might be there now. But just wait, I'll be back, and I'll be in charge again. They'll see.
[At the hospital, Brian is lying in bed with a big cast on his ankle hanging up and was reading a novel]
Brian: Come in.
[Inside comes a tall white nurse unicorn with Teal mane]
Brian: Who are you?
White unicorn: Just a visitor, and my friends are right behind me.
[then a comes a black smokey trail]
Brian: What is this?
[and then the trail swirls around and shuts the door as the Unicorn mare casts a sound proof spell in the room and then from the smokey trail appears Nightmare Moon and King Sombra, and then the nurse mare transforms into Chrysalis!]
Nightmare Moon: Surprised to see us, darling?
Brian: [Force grabs his pistol] What are you doing here?! And why are you trespassing my room?! You're all dead!
King Sombra: We were dead, but we're back again.
Queen Chrysalis: Besides, you can't keep beings like us down so easy.
Brian: [points his pistol at them as the laser points at the center of Nightmare Moon's helmet]
Nightmare Moon: Are you gonna kill us then?
Brian: I would certainly like to!
Queen Chrysalis: Do not worry, we are not here to cause harm. But help you.
Brian: You wanna help me?
Nightmare Moon: Yes. We understand your feelings, especially for Sylveon.
Brian: You don't know anything about her!
King Sombra: We know. I can feel your anger, Brian. It gives you focus, makes your stronger, and makes you more attached to Sylveon.
Brian: [looks in shock, looks at his pistol for a moment. And he throws it back to his holster] What do you want from me?
Nightmare Moon: It's what Somby wants.
Brian: What is that?
King Sombra: I need your help, Brian.
Brian: Why should I help you?
Queen Chrysalis: Because, we can help you out with your own problems, and to protect the one you truley love.
Brian: What ones?
Nightmare Moon: Those Eeveelution Pokémon, but most importantly, Sylveon.
Brian: Sounds like you wanna hurt them.
Nightmare Moon: Hurt them? (Gasps) We don't wanna hurt them.
King Sombra: Because, how could we help you if we brought harm to your wife?
Brian: How did you know that?!
Nightmare Moon: Your thoughts betray you. I sense your conflict with the other Jedi and your relationship with her. As well as great fear of losing her.
Brian: (as Cale Tucker) No! I don't believe that!
Queen Chrysalis: Then, why are you acting so tense about it?
Brian: Because of you! [deploys his Lightsaber] Now get out of here!
King Sombra: Very well, if you insist.
Nightmare Moon: Here, take this. [hands him over something]
Brian: What is this?
Nightmare Moon: A card. Just contact us if you change your mind.
[then in a thick cloud of purple and black smoke, they disappear]
Brian: [looks at the card] [sighs] Why would they want me for their dirty work? [scoffs] I think they must be crazy.
Sylveon: [in unsion] Brian!
Brian: [gasps] (he hides the card in in his novel)
[Sylveon then bursts into the room and then peeks his cheek]
Sylveon: Thomas told me what happened, are you okay?
Brian: Yeah, yeah. I'm fine, I'm fine, I'm fine.
Sylveon: Are you sure?
Brian: Yeah, relax.