Here are some of the many Rick and Morty theories.
The Original Rick has been dead the whole time/C137 Rick is not the Original Rick[]
Remember how Rick has memories of a baby Morty? How is that even possible? Rick shouldn't even have those memories. Even in the intro, it seems a little odd that in the intro, he leaves behind Morty to die at the hands of those monster frogs. What am I trying to say here?
The Talking Cat in "Claw and Hoarder...", is actually telepathic.[]
Whenever the cat is communicating, his lips never move. In fact, during one scene, his mouth is actually busy as he's licking himself at the same time as we hear his voice. In the scene on the yacht, it seemed not everyone heard him. No one including Rick seems to notice the non-moving lips. There is no clue to his origin, yet he appears in an episode in which the main adventure happens in a magical dimension. It's possible that somehow, he slipped into R&M's reality with the other characters at the time they teleported back with the Wizard and Dragon. Or, I could be over thinking it.
The Pickle Rick Dubstep Remix is canon[]
The trap remix by Oscar Santos is a canon continuity in Rick and Morty. Mainly because, I'm Pickle Ri-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-ck, I'm Pickle Ri-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-ck, I'm Pickle Ri-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-ck, I'm Pickle Ri-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-ck, I'm Pickle Ri-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-ck, I'm Pickle Ri-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-ck, I'm Pickle Ri-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-ck, I'm Pickle Ri-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-ck, I'm Pickle Ri-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-ck, I'm Pickle Ri-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-ck, I'm Pickle Ri-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-ck, I'm Pickle Ri-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-ck, I'm Pickle Ri-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-i-ck.
Explained in "Pickle Rick Trap Remix" https://youtu.be/vO9h5aAI-P0?si=So5rq53V_aQR4fgI