This is how Megatronus arrives goes in My Little Pony: Megatronus' Revenge.
[Ryvine and Rothbart are relaxing on a beach]
Unknown voice: Ryvine and Rothbart.
[A piece of metal on the floor glows and they see a head without a face on]
Megatronus Prime: Call not to your allies. I speak to you two and you two alone.
Rothbart: Who are you and how did you know me and my friend?
Megatronus Prime: I am the First Decepticon and I've always been watching you.
Ryvine Sparkle: Wow. Name's Ryvine Sparkle, leader of the Decepticons and student of Unicron.
Megatronus Prime: Cool.
Rothbart: You are responsible for the Alchemor's crash?
Megatronus Prime: Yes, Rothbart. Lover of Princess Odette.
Ryvine Sparkle: If you are the First Decepticon, how come Megatron started the war on Cybertron?
Megatronus Prime: He didn't. I did.
Ryvine Sparkle: Wait a minute. You started that war!?
Megatronus Prime: Yes. I am and always will be the founder of the Decepticons.
Rothbart: Ryvine. You got one too many hits on the head with the Forge of Solus Prime.
Megatronus Prime: What?! What did you say?!
Rothbart: Uhh. Nothing. Nothing.
Megatronus Prime: That's what I thought.
Ryvine Sparkle: If Ryan is a Prime, we would make him pay for Solus Prime's death.
Megatronus Prime: WHAT DID YOU SAY?!
Ryvine Sparkle: I said Sol... uhhh. I think we will see you on Earth.
Megatronus Prime: Earth. Oh how much I want to make both it and Cybertron pay for my humiliating exile.
Rothbart: Cybertron. That's the planet where you were betrayed by the Primes.
Megatronus Prime: Yes. For millennia, I have dreamed of my return to that wretched planet, where I was once betrayed by the Primes I called my brothers and sister. Only a Prime can defeat me and now only three remain.
Ryvine Sparkle: Rianna, Ryan, and Optimus.
Rothbart: Ryan is a friend of Odette.
Megatronus Prime: Besides that, I've got my optics set on a new target: Princess Twilight Sparkle.
Ryvine Sparkle: But one thing. How can you help us get you to Earth?
Megatronus Prime: I'm stuck in an alternate dimension.
Rothbart: Ryan protects Twilight as well.
Ryvine Sparkle: From me, Tirek, and Thunderwing, some buddies of mine.
Megatronus Prime: Thunderwing? Who is this Thunderwing?
Rothbart: Ryvine's friend. Anyhow. What do we do?
Megatronus Prime: You two are to repair my gateway. I will provide you instructions.
Ryvine Sparkle: I take orders from no one.
Megatronus Prime: You will obey. Just because I'm in a different dimension, does not mean I cannot hurt you.
[The metal plate gets scrunched up]
Ryvine Sparkle: You can play your little tricks all you like. But, I am brave. Soon, my sister, Twivine and I will have new Decepticons that no bot or hero will mess up my plans to rule Equestria and this world.
Rothbart: And when I marry Odette, everything her father owns, everything her father loves, will be mine.
Megatronus Prime: I appreciate your ambitions and Rothbart's love for Odette, Ryvine. Truley, I do. Prepare my way and I shall give you these worlds and Odette for Rothbart.
[Ryvine and Rothbart think]
Ryvine Sparkle: It's a deal.
[the metal ball falls on the sand]
Rothbart: At least for now.
Ryvine Sparkle: That's something Steeljaw said in the episode "Battlegrounds, Part 1".
Rothbart: I think that show is cool. Who is Steeljaw?
Ryvine Sparkle: Steeljaw's a Decepticon with the head and tail of a wolf.
Ryvine Sparkle: Yeah. How did you know about Odette and Ryan?
Rothbart: We've encountered them before, remember?
Crash Bandicoot: I will stop this thing before it starts!
[The gateway explodes. When the smoke clears, The Fallen is seen standing]
Crash Bandicoot: It can't be.
[The Fallen's battle helmet moves up and reveals his face]
Megatronus Prime: But it is. At long last, Megatronus, better known as The Fallen, stands triumphant!
Ryvine Sparkle: Welcome to Earth, Megatronus. I, the Decepticons' leader and Rothbart's friend knew you came.
Matau T. Monkey: [pulls out his walkie-talkie] Fixit? You think this Megatronus also known by the name of Master Ryan's student, Megatron?
Fixit: No, Matau. Megatron named himself after Megatronus. Megatronus was one of the Thirteen original Primes. But, he turned on his brethren, destroying Solus Prime.
Crash Bandicoot: Solus Prime?