The Whirly Dirly Conspiracy - S3-E5
Continuity mistake: When Beth glues the horse hoof on, the bottom is facing up. In the next shot it facing to the side. And then the leg changes shape in different shots.
Continuity mistake: After Rick and Morty have wiped their minds, Rick is looking over the broken test tubes containing the memories and then picks up a test tube with purple fluid in it, but in the next shot, the fluid is blue.
Pickle Rick - S3-E3
Continuity mistake: When Pickle Rick is waiting for the elevator to arrive, he is standing on the first floor tile directly in front of the elevator door. Once the elevator door opens, he is suddenly standing several floor tiles away from the door.
Continuity mistake: Rick traps Morty and Summer into huge soap bubbles along with their phones. The phones are no longer trapped when they reach their destination. (00:00:45 - 02:58:00)
Answer: C-137 is the dimension they came from since the pilot. After C-137 is Chronenberg'd, Rick and Morty travel to a replacement dimension that we haven't found out the designation of (although they may have moved dimensions again). The "original" Jerry, Beth, and Summer are still on C-137 though.
Bishop73