Here's how Stuingtion's Engines tell our heroes about Megatrain in Thomas' Place as a Prime.
Percy: Poor Thomas, I wish he could find his place as a Prime.
Princess Celestia: His time well be coming soon.
Mucker: Too bad Megatrain's not here. Thomas could defeat him and find his place in no time.
Princess Luna: Megatrain?
Brian: Who the heck is Megatrain?
Steamy: That's right, you guys ain't familar with thangs' from Cartoon World.
Brian: Well, what does he look like?
Mucker: He does look a bit like Spencer.
J.J.: Yeah, but with a different color scheme.
Spencer: Blistering Boilers!
Princess Celestia: Just, hold on there. Start from the top. Firstly, who is Megatrain?
[Soon "Legend/Altomare (from Pokemon Heroes)" starts playing]
Uray: Well, Megatrain is a super powerful Deceptitrain and the leader of all Deceptitrains.
Gustis: Thousands of years ago, the original Transformers landed on Earth. All of them were Primes, and they spawned the race known as transformers. Yet one of the Primes now known as The Fallen defied an important rule, and ignored the value of life beside his, thus creating the war of the transformers. The Fallen and his corrupted followers were known as the Decepticons, while the remaining Primes became Autobots. But there were some Primes known as Train-Primes, who lead the Trainbots.
Tune: The Train-Primes had folowed the rule of the Primes but Megatrain hated this rule. He was on a mission to start up a machine that would bring back his army of Deceptitrains from the dead. He was very powerful though, and he was a highly skilled fighter. He slaughtered all Primes except one, who was still to be yet discovered.
Rings: He returned to Cybertron and made a deal with Megatron, when he returned to Earth he intended to find the machine. But we helped the Autobots and Trainbots defeat him.
Evan: After that. He wasn't seen or heard from again.
Cadance: What happened to him?
Steam Driller: Nobody knows.
Brian: What are you talking about?
Dusten: He disappeared 10 years ago, and no one's seen him since.
Puffy: But we think he'll return!
Sharky: We just don't know how he will.
Brian: But how can you defeat him?
Steam Claw D.: Only a Train-Prime can defeat Megatrain.
Cleveland: But Thomas isn't a Prime yet.
Ironhide: Technecoly, he is Clevaland. But he can't transform like Optimus can.
Wreck-it Ralph: Then, it's a good thing Megatrain's not here.
Steamy: We can't be sure Ralphie.
Mako: But something tells me, someone else will come back, but not Megatrain.
Vanellope: Uh, how powerful exactaly are Deceptitrains?
Zip: Well, one Deceptitrain alone is equal to 3 Decepticons.
Zip: Yep, as serious as I can be.
Fix-it Felix: Is that the same for Trainbots and Autobots?
Sargeant Calhoun: How many troops are there in Megatrain's army exactly?
Mako; Um, a few.
Brian: A few? That dosen't seem right.
Shining Armor: Define "a few."
Mucker: Actually, it's more like a few thousand.
Rainobw: A FEW THOUSAND?!
Brian: Are you damn serious?!
Mucker: Yeah, unless you got Trainbots on your side. You're screwed.
Princess Luna: Then it's best if we try to locate some Tranbots.
Brian: Yeah, I agree on that.