This is how Thunderwing's return goes in My Little Pony Transformers Prime: Friendship is Magic.
[That night, at Ponyville town hall]
Twilight Sparkle: I hope the prophecy doesn't come true.
Optimus Prime: We can only hope, Twilight.
[Mayor Mare appears]
Mayor Mare: Fillies and gentlecolts
[The ponies glance at each other]
Mayor Mare: We are here to honor two very special ponies.
[Fluttershy turns to a bird choir]
Ratchet: I'm certain they are.
[They begin singing]
Mayor Mare: Princess Celestia and Princess Luna!
[The curtain is raised but the Princesses aren't there]
Bumblebee: [beeps] (translation: What the...?)
Twilight Sparkle: What's going on?
Optimus Prime: I do not know.
[The crowd murmurs]
Mayor Mare: Everypony remain calm. There must be an explaination.
Pinkie Pie: Are they hiding?
Smokescreen: Or are they busy right now?
Rarity: They're gone!
Bumblebee: [beeps] (translation: They've vanished!)
Pinkie Pie: Oh. That's it. They're good. [screams]
Smokescreen: What the...?
[Twilight looks at the moon to see the stars closing in and the sky flashes and Thunderwing's face disappears from its surface. Twilight looks worried]
Optimus Prime: Oh, dear.
[A swirl of purple liquid flows onto the balcony and grows bigger, taking the form of a giant Transformer]
Twilight Sparkle: Oh no. Thunderwing.
[The purple liquid glows and becomes Thunderwing himself]
Thunderwing: Ah, so good to be back. [to the Equines] Greetings, Equines. It has been a long time since I have seen your little princess loving faces.
Rainbow Dash: What have you done with our princesses?
[Rainbow Dash tries to attack Thunderwing but Applejack grabs her by the tail with her teeth]
Applejack: Whoa there, Nelly.
Thunderwing: [laughs] Why, am I not royal enough for you? Do you know who I am?
Pinkie Pie: Ooh, ooh, more guessing games! Um, how about General Bat-Wing, or how about King Blade-Arm or Blue Small Head! Blue Small Head!
[Pinkie Pie gets an apple shoved in her mouth]
Thunderwing: Does my image no longer count, now that I have been imprisoned for a thousand years? Did you not recall the legend? Did you not see the signs?
Twilight Sparkle: We did!
[Thunderwing looks down and sees Optimus and Twilight glaring at him]
Twilight Sparkle: And we know who you are. You're the Cybertronian In The Moon: Thunderwing!
[While the crowd murmurs, Thunderwing laughs]
Thunderwing: Well, well, well, an Alicorn and a Prime still remember me. Then you must know why I'm here.
Twilight Sparkle: You're here to...To...
Optimus Prime: Sorry, my friend here seems to be too nervous to bring up why you're here.
Thunderwing: Remember this day, little ponies, for it was your last. From this moment forth, Luna's night will last forever and all of Equestria will plunge into chaos!
[Thunderwing laughs evilly as clouds fill the sky and lightning crackles around him]
Mayor Mare: Seize him! Only he knows where the Princesses are!
[Some white pegasus guards fly towards Thunderwing, who sees them coming]
Thunderwing: Stay back, you foals!
[Thunderwing shoots them with lightning while laughing then unfurls his wings and flies away as the Equines below him scream in terror as he flies by. Rainbow Dash manages to free herself from Applejack's grip and chases Thunderwing as he flies out of the main entrance and into the sky]
Rainbow Dash: Hey! Get back here! Night time forever and chaos in Equestria?
[She sees Optimus drive off with Twilight and Spike]
Rainbow Dash: Wait. Where are they going?
[At Twilight's castle, Spike sleeps in a basket]
Spike: We've got to stop Thunder... [falls asleep]
Twilight Sparkle: You've been up all night, Spike.
Optimus Prime: You are a baby dragon after all.
[He and Twilight leave. In the castle library, Twilight searches through books]
Twilight Sparkle: Elements! Elements! Elements! Oh, how are we supposed to stop Thunderwing without the Elements of Harmony?
[Rainbow Dash appears]
Rainbow Dash: And just what are the Elements of Harmony? And how did you and your robot buddy know about Thunderwing? Are you two spies? Huh?
[Applejack pulls her away]
Applejack: Simmer down, Sally. They ain't no spies. But they sure know what's going on. Don't you, guys?
[Optimus and Twilight look at each other and nod]
Twilight Sparkle: We read the prophecy of Thunderwing's return.
Optimus Prime: And the only way to stop is the Element of Harmony.
Pinkie Pie: The Elements of Harmony: A Reference Guide.
Twilight Sparkle: How did you find this?
Optimus Prime: And how did you do it so fast?
Pinkie Pie: It was under E.
Smokescreen: I actually told her where it was.
Twilight Sparkle: [reads] There are six Elements of Harmony, but only five are known: Kindness, Laughter, Generosity, Honesty and Loyalty.
Optimus Prime: [reads] The sixth is a complete mystery. It is said, the last known location of the five elements was in the ancient castle of the royal pony sisters.
[As they read, a purple liquid floats by the window and then leaves]
Twilight Sparkle: [reads] It is located in what is now--
[They stand outside the Everfree Forest]
Everypony: The Everfree Forest!
[They stare into it]
Pinkie Pie: Whee! Let's go!
Smokescreen: Come on, bots!
[Twilight stops them]
Twilight Sparkle: Not so fast. Look, I appreciate the offer, but I'd really rather do this on my own with Optimus.
Optimus Prime: Yes, you Autobots need to stay here and watch over these ponies.
Applejack: No can do, sugarcube. We sure ain't letting any friend of ours go into that creepy place alone. We're sticking to you like caramel on a candy apple.
Bulkhead: And we ain't sticking around without a Prime.
Pinkie Pie: Especially if there's candy apples in there.
[Everyone glances at her]
Pinkie Pie: What? Those things are good.
Smokescreen: I'm sure they are.
Twilight Sparkle: [sigh]
Optimus Prime: Fine. You may come. But stay close beside us and do exactly what we say.
[They head into the forest]