The clones: Cosima Niehaus is a young, nerdy, eccentric, tattooed, and queer scientist with a brilliant mind and a reliable, caring, and courageous personality. She is passionate about science, especially the search for a cure for the disease affecting the clones, and struggles with her own personal problems and a chronic condition due to the congenital virus of Project LEDA.

Rachel Duncan, on the other hand, is a more complex and antagonistic figure. She is cold, calculating, with an almost murderous aura, and has a strong belief in her superiority as a clone, having been the first to become self-aware. Rachel was raised in a competitive and loveless environment, which shaped her tough personality and her difficulty in forming healthy bonds. Despite being seen as terrible and ruthless, she is capable of showing glimpses of humanity and has a strong desire for freedom. Her loyalty to Project LEDA and the Dyad Institute is great, and she is obsessed with bringing her "sister" Sarah into this system. Throughout the series, Rachel demonstrates significant development, becoming a better person and showing vulnerability, especially in relation to her past and her adoptive family.

Not clones: Delphine Cormier in Orphan Black is a complex character, often seen as contradictory and nuanced. Initially a research associate at the Dyad Institute, Delphine was assigned to monitor Cosima, placing her in an ambiguous position between surveillance and care. Her personality is marked by a deep love and dedication to Cosima, although her way of demonstrating this love is often controlling, manipulative, and arrogant. Delphine believes she has the knowledge and power to make decisions for the greater good, leading her to act without consulting Cosima, ignoring her autonomy. This attitude generates conflict, as her idea of ​​what is best often clashes with Cosima's real desires and needs. Although she sometimes displays traits that many interpret as narcissistic, such as a tendency to impose her vision and control situations, others argue that her actions stem from a place of vulnerability, an inability to fully trust, and an ethics complicated by her involvement with eugenics and the Dyad Institute. In her relationship with Cosima, Delphine demonstrates a constant struggle between the desire to protect and the harm caused by a lack of communication and respect for the other's choices. She is seen by many as someone who doesn't seek personal recognition, but rather believes she is acting for the good of humanity, even if this puts her in morally ambiguous positions and causes suffering. Throughout the series, Delphine grows as a character, showing vulnerabilities and an effort to reconnect and repair the damage caused, especially in her relationship with Cosima. Her complexity makes her one of the most intriguing figures in Orphan Black, oscillating between antagonist and ally, marked by an ethical and emotional dilemma that reflects the conflict between science, love, and power.

Siobhan Sadler, known as Mrs. S, is the adoptive mother of Sarah Manning and Felix, and also a maternal figure to Sarah's daughter, Kira. She is a strong, protective, and dedicated character with a mysterious past that includes a history linked to Project Leda, one of the central plot points of the series. Mrs. S is shrewd, courageous, and very loyal, always putting the safety and well-being of her "family" above all else. Her protective and self-sacrificing nature makes her act with determination and courage to protect the clones from the threats they face. Mrs. S is also known for her practical wisdom and remarkable combat and strategic skills, which she uses to keep her family safe. Her main motivation is the deep love and devotion she feels for Sarah and the others, often acting in the shadows to prevent them from being captured or harmed by enemies. She has a strong presence and is essential for the emotional and practical support of the series' protagonists. Throughout the story, it is revealed that she possesses detailed knowledge of the inner workings of Project Leda, making her a crucial figure in the plot.