Optimus was busy on a mission fighting Megatron like usual. They were giving each other insults out of pure comedy mid-fight...and also to annoy one another

Optimus: "Megatron, we meet again"

Megatron: "Indeed we do, Prime.."

Optimus: "Megatron the weak, Megatron the Skrunkly"

Megatron: "I- what?? You know what? Two can play at that game! Optimus the lame. Optimum Pride. Autism Prime. Optimistic Pyramid"

Optimus: "what the frag Megatron the last three didn't even make sense?"