This is how Post credits: Ryvine's Decepticons goes in My Little Pony: Megatronus' Revenge.
[We see Cortex in his lab when Ryvine and Rothbart arrive]
Dr. Neo Cortex: Ryvine. You and Rothbart are here.
Ryvine Sparkle: At least my sister is with me and Rothbart.
Rothbart: Megatronus Prime is no more, Cortex. Killed by Ryan the Prime-prince.
Ryvine Sparkle: No matter, Rothbart. Soon, the Phantom Thieves and their friends will feel my wrath.
[The villains transported to the Fallen's throne room]
Starscream: Ahh. The Fallen's throne.
Ryvine Sparkle: MY throne!
Starscream: What? After Rothbart's plans to...
[Rothbart readies his magic]
Starscream: I heed and I obey, Lord Ryvine.
Ryvine Sparkle: Cool. Serve me and we will see the downfall of the Autobots and the return of Megatron, Starscream.
Starscream: I've heard this before.
Ryvine Sparkle: But. We don't have access to this base before, Starscream. This base. Our recruits and the base's waiting army.