Spoiler Level: High
Megatron is finally on his way back. And ironically, it looks like the Autobots are going to help him get there.
When Optimus gets infected with a plague created centuries ago by Megatron, the Autobots have no choice but to send a team to hack into Megatron's mind and find the cure... which has the nasty side-effect of stirring his mind back to consciousness. It's a delightful irony that in order to save their leader they inadvertently save their enemy's leader as well.
It's also a nice way to give Bumblebee the spotlight, despite his not really being able to talk. Pingu is a great example of how a character doesn't need to really speak a real language for you to understand what they're saying, and Bumblebee not only shows that well here, he has the same innocent charm as Pingu.
One question-- I get that Transformers can create plagues that affect machines, but can you really call it biological warfare then?
As usual, this episode is currently available to watch for free at http://www.hubworld.com/transformers/shows/prime/videos.