This is how Optimus and Twilight see Megatronus turn into Megatron goes in Princess Twilight Sparkle.
[Twilight and Optimus find themselves on Cybertron in the middle of Iacon]
Twilight Sparkle: Iacon!
Optimus Prime: But how? I thought it was destroyed in the war.
[Megatronus' voice comes out of nowhere]
Megatronus: Not another step. [comes out of the shadows]
Twilight Sparkle: Megatronus!
Optimus Prime: We do not understand brother. What's going on? Why are we here? How? How did Princess Celestia and Luna disappear?
Megatronus: Did you really expect me to lay idle by while you were chosen to be the next in line?
Twilight Sparkle: Next in line?
Optimus Prime: What are you talking about?
Megatronus: There can only be one powerful being on Cybertron! And that powerful being will be I!
[Megatronus turns into Megatron]
Twilight Sparkle: [gasps]
Optimus Prime: Megatron!
[Megatron blasts the roof and Optimus and Twilight duck out of the way just as Orion Pax arrives]
Orion Pax: Megatronus. I will not fight you. You must remain a gladiator. It is your duty.
Megatron: Megatronus? I am Megatron! And I have one duty now. To destroy you! And all who stand in my way! [shoots at Orion]
[Orion Pax gets out of the way as Megatron blasts a hole in the wall. Orion Pax runs through the hole, transforms and drives off]
Megatron: And just where do you think you're going? [transforms and follows Orion]
[Optimus transforms too and Twilight gets in. They race after the two as Megatron tries to blast Orion, missing several times before getting a direct hit to Orion's chest. Orion screams in pain as he falls to the ground]
Twilight Sparkle: Oh, no!
Optimus Prime: Orion!
[They go after him as Megatron laughs triumphantly. Optimus and Twilight arrive near the seemingly dead Orion Pax]
Twilight Sparkle: No. No.
Optimus Prime: Why would Megatron do this? Why now?
[As they cry softly, Orion gets up and stands, making them gasp in awe]
Orion Pax: My brother. I am sorry. But you have given me no choice but to use this!
[Orion holds up the Matrix of Leadership]
[Orion puts the Matrix in his chest and turns into Optimus Prime]
[Megatron tries to blast Optimus but his beam is stronger and Megatron is defeated]