When Optimus thought he was Orion Pax aboard the Decepticon warship:

Optimus: "Why is your ship so dreary?"

Megatron: ...

Optimus: "Why is your army so gloomy?"

Megatron: :T

Optimus: "Megatronus... why are you called Megatron now?"

Megatron: GRRR! QUIT ASKING QUESTIONS!" *glares at him*

Optimus: "Why are your eyes so RED?"

Megatron: *points at him* "Listen you-"

Optimus: "Why are your fingers so sharp?"

Megatron: "STOP IT OPTIMUS!"

Optimus: "Why did you call me that?"

Megatron: -_- *slams head against the wall*