AERYN SUN 
If what happens aboard Moya is at one point labeled as a "transformative journey", this is particularly true for Aeryn Sun: once she finds herself stranded on the Leviathan, cut off from her past, stranger in a strange land, she begins a long and often painful metamorphosis. Declared "irreversibly contaminated" by her fellow Peacekeepers, trapped with escaped criminals and facing a very uncertain future, she deals with a series of dramatic choices whose consequence is the radical transformation of her whole being, one she tries at first to resist with stubborn determination.
We see that stubbornness since the pilot episode: faced with the choice between unavoidable execution and escape with the other prisoners, still she clings to her old life ("It's what I am, it's my breeding since birth!") and only when John Crichton tells her that she can "be more" does she snap out of her hesitation. And only much later will we learn the meaningful importance of that choice of words.
From that moment on she starts the long journey that will reveal her as a person, not just a perfect soldier that lives and breathes discipline and orders; a journey that will open to her a world of feelings and attitudes that had been denied her by Peacekeeper social mores.
In this respect two are the pivotal episodes in Aeryn's story-arc: the first occurs in Season One and is DNA MAD SCIENTIST. When the insanely brilliant NamTar injects her with Pilot's DNA, her physical barriers are breached, her "racial purity" – one of the tenets of PK society – broken forever. By her own admission Aeryn feels that the very core of her being has been changed irrevocably, that she has now truly been irreversibly contaminated as her captain declared some time before.
In Season Two, with the episode THE WAY WE WEREN'T, her emotional barriers crumble in the face of long supressed memories and a tragic revelation: Aeryn had a passionate relationship with the Leviathan scientist Velorek, who had perceived her great potential and wanted to take her away from the stifling mold of the mindless soldier. Terrified both by the intensity of the feelings she was discovering for the first time and by the prospect of a future so distant from what had been her life-long comfortable routine, she had denounced Velorek for his treason and gone back to her old unit. Not without harboring a deep-seated guilt and fear of emotional commitment. When these circumstances are revealed we understand her reaction to Crichtons' words about "being more", since this was exactly what Velorek had urged her to be.
It's easy to sympathize with Aeryn while she faces these trials that little by little dismantle the barriers she puts between herself and the outside world, and it's just as easy to share her enthusiasm when she breaks unwritten rules and manages to overcome the PK's psychological conditioning. A good example is in THANK GOD IT'S FRIDAY, AGAIN, when she successfully analyzes the compound that makes Rygel's body fluids explosive, providing the key factor in solving the situation the Moyans find themselves in. Among the Peacekeepers, tasks are strictly compartmentalized: soldiers fight and techs work in supporting roles. Her pride in overcoming this limit is almost childlike and stresses once more her stunted emotional growth, a side of Aeryn that clashes with her outward appearance, that of a fearless and competent soldier.
Interestingly, it's Pilot who urges her toward this kind of discovery: Pilot, whose DNA will mix with hers and who represents the being she is initially more attuned to on Moya. Her relationship with Pilot – even more than the one with Crichton – will help expose her softer and more feminine side and will be one of the constant links to her better instincts throughout the story arc. Somehow, Pilot is Aeryn's mirror image: he is kind and gentle but is also possessed of a strong mind-set and deep-rooted principles. This must be the main reason they find, almost from the start, a common ground ("We work together well" she tells Pilot at some point) that blossoms into a special and privileged bond.

Aeryn's character is also defined by her difficult and tormented relationship with John Crichton: their love story, one of Farscape's core themes, is the ground where her inner changes are played more deeply and is also a way to portray the romantic side of the story in a new and unconventional way, while at the same time presenting many interesting angles for discussion on the ever complex relationship between men and women.
Aeryn and John's relationship is fraught with objective difficulties and misunderstandings that come both from the universal differences between the male and female of any species and from the cultural and psychological barriers between two alien races – no matter the striking physical similarities between them. Peacekeepers are conditioned to avoid any emotional commitment, because it's considered a weakness that can impair a soldier's efficiency: they don't have the concept of family, births are decided by assignment to "fill the ranks", they entertain no stable love relationships and are allowed to "recreate" – the choice of term speaks for itself – only as a form of stress-management. Everything revolves around rules and discipline. At some point we learn that Aeryn's birth was exceptional, because she was conceived out of the clandestine and forbidden love of her parents: once discovered, they were cruelly punished – Aeryn's mother was given the choice between taking the life of her daughter or of her mate.
With these premises it's hardly surprising that John Crichton's efforts to conquer Aeryn's heart meet with such resistance and fall into the category of "one step forward, three steps back". Moreover, she often lays the rules of the "game", which is clear since their first fateful encounter, when she throws him bodily to the ground – without apparent effort – and demands for his "rank and regiment". From the start it's evident that Aeryn is the "strong" half of the couple, a role that is usually reserved to the male, and that Crichton represents the more "feminine" half, particularly in his desire to mediate and talk before recurring to brute strength. Role-reversal, in tv shows, is often relegated to the realm of humor, as if to indicate that it's a joking matter. Farscape has no fear of tackling this topic in a more serious manner.
This strong core in Aeryn's personality remains basically unaltered throughout the show, and is evident in the fundamental dignity that informs her character despite the changes effected by experiences: this trait is plain in many circumstances and is brought to the fore in one of the most dramatic moments of the saga. During Aeryn's imprisonment by the Scarrans, in Season Four, she has little or no hope of rescue – not just for herself but for the child she carries in stasis. The surprising, uncharacteristic prayer she addresses to an old Sebacean divinity is of course a sort of last resort against despair, but is also quite emblematic of the person Aeryn is: she does not ask as a supplicant at her wit's end, but as a soldier dictating conditions. She can be hurt by wayward emotions, because she's had no training or life-long acquaintance with them, but she can physically and mentally withstand almost anything.
This is one of the reasons she is such a fascinating figure, this amalgam of outer strength and inner fragility, this factual representation of a real, flesh and blood woman, with all her realistic contradictions.
Even when the love story with Crichton finally rests on firmer ground and we see them assume the role of parents, Aeryn's basic essence remains unaltered: it's impossible not to smile when we see her determined to be an active part in the defense against the Scarrans despite being racked by labor pains – "Shooting makes me feel better!" she says, and if we know this is a necessary tension-breaking line in the script, we also know it comes out of her deeper nature. As does another sentence uttered at the prospect of an hours-long delivery: "I've killed men for less!" It's a warning, a statement that shows how this woman will not be constrained into an idealized mold, or weighed down by conventions.
She is transformed by her experiences, yes, but not altered: when we look at her, towards the end of PEACEKEEPER WARS, we see her holding her newborn baby with one hand and shooting enemies with the other, with her usual, economical efficiency; stroking her child with love and dispensing death at the same time.

The discovery of feelings, love, motherhood has not changed this extraordinary character but simply added more layers to it, making it more complete. Making it *more*. This is why she is one of the most original figures of the modern sci-fi scene. And probably the best.