This is how Optimus reactivates goes in My Little Pony Transformers: Age of Extinction.
[We see Rarity come out of the castle and heading to the barn]
[We see Twilight working on a robot arm]
Twilight Sparkle: Okay, come on, come on.
[The robot arm moves perfectly]
Twilight Sparkle: Yes. Yes. Yes. Oh, there you go.
[The robot arm suddenly starts shaking]
Twilight Sparkle: No, hold it. Stop shaking! Why are you shaking? You have the job.
[Rarity comes in]
Rarity: You forgot to eat dinner. You see why I worry? [brings her a tray of food]
Twilight Sparkle: Look, sorry, Rarity. I... I almost got it working right.
Rarity: So, listen, I'm done with grading papers and set with creating the finals, so I was just gonna take ride with the girls. If that's okay with you.
Twilight Sparkle: [sighs]
Rarity: No colts. I know.
[We then see Flash looking at something in awe]
Flash Sentry: What is that? It looks like a missile.
Twilight Sparkle: It is!
[The missile suddenly comes live and launches out of Twilight's magic]
[The missile flies out of the barn]
[Rarity tries to avoid the missile]
Rarity: Twilight, there is a missile in the throne room!
[Back in the barn]
Twilight Sparkle: Sweet Celestia.
[The truck transforms into Optimus]
[He appears to freak out]
Optimus Prime: I'll kill you! No! No!
[Rarity and the girls come in]
Applejack: What in the hay?!
Rainbow Dash: What is going on?!
Pinkie Pie: RUN FOR IT!
[Optimus takes out his shotgun]
Optimus Prime: I'll kill you! Stay back!
Twilight Sparkle: Don't shoot, don't shoot!
Flash Sentry: Call 911. Go.
[Flash tries to run but is hit]
Optimus Prime: Easy.
Twilight Sparkle: [to Flash] Don't move. [to Optimus] Optimus, it's me, Twilight Sparkle.
Optimus Prime: Twilight, thank goodness you're alright.
[He tries to get up]
Optimus Prime: Weapons systems damaged.
Twilight Sparkle: A missile hit your engine. We took it out, You're in bad shape. You're at my castle.
Optimus Prime: Twilight, I'm in your debt. My Autobots, they're in danger. [parts fall off of him] I need to go. I need to go now.
Twilight Sparkle: How far you think you're gonna get? Rarity, come here, he needs our help. What happened to you?
Optimus Prime: Ambushed, a trap set by Equestrian mercenaries. I escaped and took this form. [coughs]
Rarity: But you're on our side, why would Equestrian hired guns working for the government hurt you?
Optimus Prime: They were not alone. My Autobots can repair me.
Twilight Sparkle: Yeah, if you can get to them. What about me?