Optimus heard the muttered comment down the hall. As he's the only prime - that he's aware of - on board at the moment (since even Sentinel kind of doesn't count at present), he's naturally drawn to see who's talking about him.

He rounds a corner only to pull up short in shock at the apparent newcomer. Well, at the SIZE of the newcomer.

"Ah . . . greetings . . . ?"

If he's honest, there's a small corner of his processor that's stuck on repeat - please be Autobot, please be Autobot, we don't need problems this big...