As a Fridge subpage, all spoilers are unmarked as per policy. You Have Been Warned.
- When Leekie says that Cosima could end up on the cover of Scientific American, she replies that they don't put scientists on the cover. Leekie covers, but it's obvious he was referring to her as an experiment, not a scientist. He knows she's one of his clones.
- The Dyad monitors the clones by having agents form relationships with them; thus forming a dyad, a two-person social group.
- Why is Helena wearing Sarah's shirt in the finale? Because she stole it when she broke into Beth's apartment.
- Mirrors and windows appear frequently in the cinematography. By their very nature, mirrors reflect one's own image and windows provide glimpses into the truth. Fitting for a show about identity and secrets.
- Sarah looks into or is reflected by mirrors three times in the premier, each of which has to deal with her taking on a new persona: in the restroom after she steals Beth's purse, during her transformation into Beth, and in the precinct bathroom when she realizes being Beth will take a lot more commitment than she expected.
- When Katja is murdered, the bullet shatters the car windshield, representing how Sarah's "normal" life had been irreversibly changed.
- Rachel is often shown in front of windows, and she is the only clone that was raised self-aware and knew (part of) the truth about her origins from the start.
- The references to Classical Mythology
- The two cloning projects are named Leda and Castor. Protect Castor was an offshoot of Project Leda, just like in the myths, where Castor is Leda's son.
- Helena is one of the clones produced by Project Leda. Helen of Troy was one of Leda's daughters.
- Helena refers to Ethan Duncan, one of the creators of Project Leda, as "Swan Man". Zeus impregnated Leda under the guise of a swan.
- Cal jokingly guesses that Sarah is a Pisces. In mythology, Pisces represents the fish that Aphrodite and her son Eros turned into to hide from Typhon. A mother and her child running from a monster? Sounds just like what Sarah and Kira have been doing for the whole of season two. It's worth noting that Sarah and Kira are wanted by the Proletheans, whose symbol is a fish with wings.
- In some versions of the myth, Castor is the mortal son of Tyndareus and Pollux is the demigod son of Zeus. By season 5, the Neolutionists decide that the Leda clones are more important, making them the "divine" siblings, while the Castor clones are now disposable. The myths usually end with Castor dying and his divine sibling Pollux being spared, so by the end of the series all the Castor clones have perished, while the surviving Leda clones find a cure.
- This show has a lot of fish symbolism, especially in regard to Helena. In several cultures, fish are a symbol of fertility and Helena is one of the two clones capable of having children, the other being her twin sister Sarah. Speaking of which, fish are also associated with partnership, such as Pisces (mentioned above) and koi fish swimming in pairs. Fish are closely connected with water, for obvious reasons, and water is often associated with the creation and sustenance of life, change and adaptability, and exploration of the unknown — themes that are all prominently featured in this series. Finally, there is a Christian element, the Ichthys ("Jesus Fish"); Helena was raised in a convent and the Prolethians are Fundamentalist Christians.
- The main clones each represent various institutions: Beth, the law; Alison, social obligations; Cosima, academia; Helena, religion; Rachel, corporations. Quite conspicuously, Sarah not only lacks ties to any institutions, but goes against the institutions that her sisters represent. She's a criminal, she's left her family and friends multiple times, she never finished school, she's not religious, and she refuses to cooperate with the Dyad Institute.
- Cosima is the most individualistic and genuinely authentic of the clones. When it comes time for her to impersonate Alison, this naturally makes her the worst impostor of the lot.
- In 4x07, Rachel hallucinates a swan. In the very next episode, she begins reaching out to her fellow Leda clones, partially as a reaction to her failing health and partially because Evie Cho has threatened them. The myth of Leda, of course, heavily features a swan, so it's quite possible that her hallucination of the swan represents her acceptance of who she is.
- When Leeky gets Sarah's test results back, he immediately tells Olivier that she's not Beth, but dodges the question when asked which one she is. This is because Sarah and Helena are twins, so they are genuinely identical and don't have the different genetic ID tags like all the other clones. Note that later, when Leeky is told that Helena has been impersonating Beth, he immediately realizes that it was actually Sarah; it had to be one of the two, and obviously it wasn't Helena because she's "practically feral."
- In the series finale, Helena talks about how every time she turns around, she finds one of her babies eating sand, and she has no idea where the sand even comes from. At first, this just seems like Rule of Funny. But when you think about it, Helena spent roughly half of Season 3 trapped by Castor in the middle of a desert. Depending on how often (or how thoroughly) she washes her hair, the sand could still be left over from her time at Castor headquarters.
- In episode of nine of season one, there's a brief glance at the back of Sarah's head, where one section of her hair is very wavy. Almost as wavy as Helena's hair. Considering we see Sarah's hair curl up when it's wet, it makes a lot of sense that she might blow dry it straight, and that Beth (and others) flat-iron it. Since they do have some differences like Cosima needing glasses, Helena's hair texture could be what their hair would look like at the extreme end, and possibly not a perm. Cosima's hair, as well, could even be curlier. Her locs look much like locs on people with coyly hair, not the matted chunks that most white people have when they try to do that hairstyle (as straight hair won't stick together like that without being very damaged and unwashed).
- While not addressed, there's no reason that the psychic/empathic link between the LEDA clones wouldn't also be shared between the CASTOR clones, and that potentially there would be a connection between all of them. It would explain why the brothers synced so well together in their military environment (and why, even raised apart, Ira was drawn to learn more about them). It would also explain why the sisters felt a connection to their brothers. Sarah and Mark protect each other a few times even though they don't necessarily like each other, Cosima grows to have concern for Ira while on the island, and even Rachel develops enough empathy for Ira that she doesn't harm him in the same corporate coup where she stabs her own mother.
- Aynsley wasn't Alison's monitor. She really was trying to be Alison's friend, and Alison alienated her and allowed her to die for no good reason. As bad as Alison took it when she thought Aynsley was The Mole, how bad will it be when she learns the truth?
- As seen with Alison's arc in season 2, the answer to that question is "horribly".
- The children in the Prolethean nursery are all Hank's children. Confirmed by Word of God. It's likely that if they stay in that community, they will be abused like Helena and Gracie were.
- Considering the fact that fertility and reproductive rights become major themes in the second season, Amelia's death becomes a little harder to watch. The Dyad took advantage of her situation, so they could use her womb and years later one of the children she gave birth to, Helena, stabs her in the abdomen.
- This simple fact; this series is set in a Shared Universe with Ginger Snaps. What does that mean? Werewolves exist in this world!
- Between seasons three and five, something about being kept on Revival has made Delphine so afraid of it and Westmoreland that she seems on the edge of PTSD even when putting on a mask of willingly helping his research. It's also likely that Cosima's safety was partially leverage to ensure Delphine would come back to the island. She's clearly not being monitored by anyone from Neolution, since she can meet up with Siobhan, but Westmoreland knows that she'll come back even after being held there for months - and she's sent away on her first research mission the same day that Cosima ends up at Revival.
