WARNING: The following contains SPOILERS for Rick and Morty season 4, episode 10, "Star Mort Rickturn of the Jerri."
The Rick and Morty season 4 finale "Star Mort Rickturn of the Jerri" dropped a bombshell for long-time viewers of Adult Swim's animated comedy, confirming a mystery that has been teased since season 3: is Beth a clone? Rick and Morty season 4 brought back several characters from previous seasons, and even finally concluded the Phoenixperson story introduced in the season 3 premiere. The season 4 finale addressed the clone mystery as well — and setup a new chapter for this storyline for season 5.
The "is Beth a clone" mystery originates in the season 3 episode "The ABCs of Beth." In the episode, Rick offers to clone Beth so that she can go adventure in the cosmos. He suggests the clone can take her place in the home so that the family won't miss her. The episode never shows what Beth chose, and the following episode, "The Rickchurian Mortydate," shows Beth growing increasingly paranoid at the prospect that she may be a clone. Although she has conversations about the prospect with Rick, his response fails to adequately address the question.
The season 4 finale finally addresses the mystery — by having a second "space hero" Beth show up on Earth to confront Rick about being a clone. This Beth discovers an implant in her neck, which leads her to believe that Rick never wanted her to return to Earth, assuming the implant would detonate if she ever returned to the Smith home. After confronting Rick, however, this new adventurous Beth starts to question if she herself is the clone, and if the original Beth opted to remain home with her family.
Eventually, Rick reveals through a projected memory that he is unsure which Beth is the original and which is the clone. After the events shown in "The ABCs of Beth," Beth returned to Rick and requested that he decide for her if she should stay or if she should go adventure in the cosmos. Rick — who has spent the series shirking responsibility whenever possible — stays true to his character: he creates a clone but then uses a machine to randomly select which version of Beth would go adventure in the unknown, avoiding having to make the decision himself.
The finale ends with the revelation that there is no revelation; furthermore, the Smith family has learned to embrace the situation, making the decision to reject Rick's toxic behaviors. It's no coincidence that this episode also featured the return of family therapist Dr. Wong: the episode implies that the family have continued to see the therapist, largely without Rick's cooperation. Both versions of Beth tell him off, and Beth and Summer express excitement about having a second "badass" mom. The family's acceptance of this second Beth, and the episode's firm refusal to return to the status quo at the end of the episode, set up season 5 to feature both versions of the character — as well as a new dynamic between Rick and his daughters. Throughout Rick and Morty, Beth has allowed her abandonment issues with her father and her desperation for his acceptance to cloud her judgement regarding his behavior. Season 5 looks to change that, which will no doubt result in some interesting narrative choices.