The latest Rick and Morty fan theory suggests that Evil Morty is actually a version of Rick. While the series primarily focuses on the versions of Rick Sanchez and Morty Smith who originate from dimension C-137, the magic of Rick and Morty's multiverse premise has allowed an entire spectrum of Ricks and Mortys, such as Evil Morty. The evil version of Morty was first introduced in season one, where it was revealed that he was controlling a version of Rick through a receiver implanted in his head. He has since been elected President of The Citadel.
Even though he's only appeared in a few episodes, Evil Morty has become the subject of intense and wild theorizing by Rick and Morty fans. Since he seems to be the Rickest Morty on the Central Finite Curve, some have suggested that he could be the original Morty of C-137's Rick. Other fans have also speculated that if he's the Rickest Morty, then his Rick would be Doofus Rick, who is believed to be the Mortiest Rick. However, a new theory suggests that Evil Morty doesn't have his own Rick because he is a Rick.
The basis for this theory begins with Evil Morty's personality and characteristics that most Ricks also have. He is brilliant, cynical, and has been shown drinking alcohol, all of which is par for the course with a Rick. All of this could be chalked up to him being the Rickest Morty perhaps, but Rick and Morty has also introduced technology that could make Evil Morty being a Rick make sense. According to the theory, a version of Rick has put his consciousness in the body of a Morty, resulting in the unsuspecting form of a Morty being merged with the twisted mind of a Rick.
The technology for this mind transfer was introduced in the Rick and Morty season 2 episode "Big Trouble in Little Sanchez." To help Summer and Morty, Rick transfers his consciousness into a smaller body and poses as a high schooler. If Rick has this technology, then it is possible that others in the galaxy also know how to do this procedure themselves, especially another Rick. There has also been no evidence that suggests the transferring of a mind can only be done between the same person. This could allow for another version of Rick to put his consciousness in the body of his Morty. If this theory is correct, it could explain why Evil Morty is so similar to Ricks and knew how to act like them so well.
As fascinating as this theory is, where would this leave Rick and Morty? For starters, it would mean that a future episode of the series could reveal another version of Rick in a similar vat to the one featured in season 2. But this could also mean that Rick is the looming antagonist of the show, not an evil version of Morty. Maybe the future of Rick and Morty will lie in Rick having to track down the version of himself who has taken over the body of a Morty. It could even lead an intriguing confrontation between Rick and a version of himself that looks like the grandson he's now grown to care for. Of course, all of this is just based on a theory at this point. We'll have to wait and see if Rick and Morty season 4 provides any new hints about who Evil Morty is, and whether or not this theory could be true.