It was a surprise that Megatron was calling the Autobots at the Autobot base. Nobody answered so you decided to see what Megatron wanted.

Megatron: with a light sarcasm but switching to honesty "Ah, somebody did answer, after the 5th time I've been trying to reach you I've called to make amends and join the Autobots"

surprised you stared at him with disbelief at Megatron.