This is how our heroes discover who Yoaki really is and Ransack betrays Yoaki in Thomas and Twilight Sparkle's Adventures of Big Hero 6.
[Bumblebee punches Yoaki in the face, sending him flying and knocking off his mask. Thomas is about to blast him with his Iron Blaster when he notices that Yoaki's mask has come off, revealing him to be none other than...]
Thomas: Robert?! Alive?
Robert: [looks up] Thomas? Is that you?
Thomas: Yes it is. But how come you're alive?
Robert: You see, [flashes back to the day the explosion happened] When the explosion happened, I used Hiro's microbes to protect me from it. Everyone believed I was dead, but that is not true. You never knew this, until now.
Thomas: [gasps] Wait a second! You were the one who made the explosion happen the other day, not someone else!
Robert: Yes. [puts his mask back on] [as Yoaki] Now, you may no longer call me Robert, but Yoaki!
Ransack: No! [jumps on Yoaki, knocking him over]
Yoaki: [tries to shake off Ransack] Get off me you fool!
Hiro: I don't understand! Why would one of Yoaki's minions turn against him?
Ransack: [continues to beat up Yoaki] I never should HAVE TRUSTED YOU!
Bumblebee: What's he talking about?
[Ransack hits Yoaki in the face, knocking him unconscious. He then points at him]
Ransack: And this time... STAY UNCONSCIOUS!
Thomas: Why, Ransack? Why did you betray Yoaki?
Ransack: If he found out what I was up to, he would order the microbes to attack me. Plus, he's rude.
Thomas: [looks at the others who nod] Ransack, I hereby welcome you to our Adventures Team!
Ransack: Thank you, Thomas.
Rainbow Dash: There's one thing I don't quite understand, Ransack. Why do you hate Thundercracker so much?
Ransack: Because, he always insults me. He's been doing it ever since we first met.
Applejack: Ah' never knew that.
Apple Bloom: Me neither.
Optimus Prime: Now that we have Ransack on our team, what do you suggest we do next, Thomas?
Thomas: We find out what Yoaki's plan is and stop it! We have to.
Rainbow Dash: Let's take the Elements of Harmony just in case the bad guys gain the upper hand.
Thomas: That's a good idea, Rainbow.
Ratchet: Then, in order to stop Yoaki's threat, I suggest we take on our Beast Hunter personas once more.
Megatron: I too could use an upgrade.
Thomas: Then what are we waiting for? Let's do it!
Knock Out: I can use my intelligence to make suits for each and everyone of us.
James: Thanks, Knock Out.
Breakdown: Let's do this!
Everyone: Friendship is magic!