Although debuting over a decade ago in 2004, Lost remains an enduring classic of dramatic television. During its run, fans composed elaborate theories to explain the mysterious events that took place from episode to episode, the mystique of series' supernatural elements as well as the complex and labyrinthine plot. It was a phenomenon which garnered both critical and commercial acclaim.

But one of the pillars of Lost's lasting appeal is the character-driven story arcs and episodes spotlighting individual survivors on the enigmatic island somewhere in the Pacific. Clocking in at over one hundred episodes over the course of six seasons, keeping track of the characters—their mannerisms, as well as their inspirations and motivations—can be daunting. And while the series boasts a bevy of characters great and small, this list should serve as a retrospective—or “crash course,” if you'll excuse the pun—for the most significant pieces on this grand chess board of television history.

Warning: For those you who haven't seen the series, SPOILERS follow.

22. Kate

Portrayed by: Evangeline Lilly

First Appearance: Pilot (Season 1, Episode 1)

Kate's past haunts her present; her survival of Oceanic 815 crash gives her a chance to evade her past life as a fugitive of the law for murder. But Kate rarely comes across as a hardened criminal; that said, she is strong-willed and determined, capable and smart, her survival skills having been honed on the run. She later is one of the few survivors to escape from the island, and the only one to do so twice. She is part of a love triangle with Jack and Sawyer, drawn to Jack's dependability and Sawyer's wild side. Although Kate's past should color the perspective of other survivors, she is often regarded as a voice of reason and dependability.

Trivia: Originally, Jack was intended to die during the pilot, and Kate would have been cast in the “leader” role for the survivors.

21. Hurley

Portrayed by: Jorge Garcia

First Appearance: Pilot (Season 1, Episode 1)

Hugo “Hurley” Reyes is arguably the warmest, most beloved character in Lost. Possessed of a kind demeanor and general acceptance of others, he nonetheless harbors a cursed past... at least to Hurley. Prior to the crash, Hurley was both in an asylum patient and a lottery winner, both incidents tied to a series of fated numbers which reemerge for Hurley on the island, a sign that all of the coincidences are tied together in a lattice of fate controlled by some other force. It is no coincidence then, that Jacob later affords Hurley special knowledge about his grand plan. Oh, and Hurley can see and communicate with ghosts.

Trivia: Season 2 introduced a love interest for Hurley in the form of Libby (Cynthia Watros), a clinical psychologist who also happened to attend the same mental institution Hurley attended.

20. Charlie

Portrayed by: Dominic Monaghan

First Appearance: Pilot (Season 1, Episode 1)

Bass guitarist for a rock band called Drive Shaft, Charlie Pace is one of the first characters explored in Lost. Revealed to be a heroin addict early on, some of his biggest struggles in season 1 involve him concealing his addiction from the other survivors, something which Locke ultimately helps him overcome. Charlie falls in love with Claire, who returns the affection, and he takes the role of a father for her newborn son, Aaron, while they are on the island. His fate is twice foreseen by Desmond, the second instance showing his ultimate sacrifice on the Dharma station called “The Looking Glass.”

Trivia: Charlie's rock and roll background comes in handy when a musical combination to disable a jamming device requires him to recall The Beach Boys' “Good Vibrations.”

19. Desmond

Portrayed by: Henry Ian Cusick

First Appearance: Man of Science, Man of Faith (Season 2, Episode 1)

First revealed to be the “man in the hatch” discovered by Jack and Locke during season 1, he has been consigned to enter a series of numbers into a computer every 108 minutes to “prevent the end of the world;” and his adventures only get more interesting from here. Desmond is the equivalent of an “X Factor” for the story of Lost, a karmic wild card who often finds himself at the center of everything from time travel, the first individual capable of discerning the true nature of the “flash-sideways” in season 6, and being acquainted with people like Charles Widmore (Alan Dale), whose involvement in the Dharma Initiative directly influences events on the island. When Desmond is involved, big things happen.

Trivia: Desmond's comment to Jack shortly after they first meet, “see you in another life, brother,” takes on a whole new level of irony in season 6.

18. Mr. Eko

Portrayed by: Adewale Akinnuoye-Agbaje

First Appearance: Adrift (Season 2, Episode 2)

A member of the “tailies,” the name given to the survivors of the Oceanic 815 crash from the tail section, Mr. Eko is one the most mysterious characters of Lost, prior to his flashback episode, “The 23rd Psalm.” A man of few words—fewer following the tailies ambush by the Others, and Mr. Eko's killing of two of them, where he forces a penance of silence upon himself—Mr. Eko has a faith he has reclaimed following his dark past in Nigeria as a drug lord. His guilt spurs him into posing as the priest his deceased brother Yemi (Adetokumboh M'Cormack) was, who tried to turn him away from his wicked ways. Mr. Eko's faith in the mysteries of the island sometimes puts him at odds with characters like Locke, but motivates him to build a church on the island with Charlie's help.

Trivia: The Beechcraft aircraft in the jungle, first appearing in “Deus Ex Machina,” was the plane Mr. Eko's brother was on when it crashed, upon which Mr. Eko was originally intended to be a passenger.

17. Richard Alpert

Portrayed by: Nestor Carbonell

First Appearance: Not in Portland (Season 3, Episode 7)

Among the already interesting and diverse characters in Lost, Richard is one of the most unusual by virtue of his gifts and his origin. Hailing from the Canary Islands in the 19th century, Ricardo (as he was called) was a man convicted of the murder of a doctor, sentenced to death, sold into slavery, and then shipwrecked on the island. He is one of the earliest examples of a pawn in the battle of good and evil between Jacob and the Man in Black, and as such was gifted with immortality. He remains one of Lost's greatest mysteries, since he always appears the same age between flashbacks and timelines as far back as 1954, a detail which should rightly unsettle viewers.

Trivia: Nestor Carbonell is fluent in Spanish, a skill which he was able to put to use in Richard's origin episode, “Ab Aeterno.”

16. Michael and Walt

Portrayed by: Harold Perrineau (Michael) and Malcolm David Kelley (Walt)

First Appearance: Pilot (Season 1, Episode 1)

Father and son, Michael and Walt both take part in some of the bigger twists in the already complex story of Lost. Michael's obsessive protectiveness of Walt makes him appear as domineering or shallow to his son's bigger needs. For Michael, finally gaining custody after the passing of Walt's mother means he must protect Walt at any cost, and his willingness to achieve this is foremost in his mind; everything else is expendable, a mentality tragically exploited by the Others. Walt is a bigger mystery, originally portrayed as being in tune with the supernatural elements of the island, and theorized to be one of the potential “candidates” intended by Jacob to inherit the island. Walt loves his dog, Vincent, who is featured in bookending shots in the first and last episodes of Lost.

Trivia: Michael and Walt are the first survivors to leave the island, effectively written out of the majority of the series for the most part. Popular opinion points to this being a result of Malcolm David Kelley growing old too quickly for the show, and was no longer convincing as a ten-year-old.

15. Daniel Faraday

Portrayed by: Jeremy Davies

First Appearance: The Beginning of the End (Season 4, Episode 1)

First introduced following contact with the freighter presumed to rescue the survivors, Daniel Faraday is a theoretical physicist with a focus in space-time. At first glance, he comes across as distracted, but who wouldn't be distracted when surrounded by existential paradoxes and the various manifestations of time travel? Faraday's lineage is tied inexorably to the island, his parents Eloise Hawking (Fionnula Flanagan) and Charles Widmore being the effective progenitors of the Dharma Initiative.

Faraday's presence and knowledge proves crucial to Desmond's survival following his personality flipping between time in “The Constant,” and his understanding of time and destiny makes him a scientific counterpart to Desmond in a way. His affection for fellow member of the freighter, Charlotte (Rebecca Mader), creates a closed loop of consequence, where he tries to dissuade her as a child from returning to the island, invariably propelling her on that path, reinforcing Daniel's assertion that time cannot be altered.

Trivia: The mouse which Faraday uses in order to further his studies of time-displacement is named “Eloise” after his mother.

14. Sun

Portrayed by: Yunjin Kim

First Appearance: Pilot (Season 1, Episode 1)

Sun-Hwa Kwon was always meant to be in a position of power and influence, but is introduced into Lost as a woman forced to endure the nigh-oppressive control of her husband, Jin. In Korea, Sun was born into the powerful Paik family, and was surrounded by wealth. Her marriage to Jin was troubled, and led to an affair with a former suitor and her English language coach, Jae Lee (Tony Lee), creating a double secret from her husband revealed over time on the island.

Sun escaped the island as one of the “Oceanic Six,” and assumed control of her father's company. This power afforded her some influence to directly confront those whose involvement in the affairs of the island, including Ben Linus, whom she believed was in part responsible for Jin's fate on the freighter. Sun may be unassuming at first, but she can wield an icy rage against those who cross her.

Trivia: Actress Yunjin Kim originally auditioned for the role of Kate; while that role went to Evangeline Lilly, the producers created the role of Sun specifically for her.

13. Jin

Portrayed by: Daniel Dae Kim

First Appearance: Pilot (Season 1, Episode 1)

Jin-Soo Kwon is the husband to Sun, who, unlike Sun, was not born into power and wealth, but instead into poverty, the child of a fisherman and a prostitute. His lineage a mark of shame following his courtship of Sun, he becomes an enforcer pressed into illegal and violent activity on behalf of Sun's father. Jin's path into darkness is largely unknown to Sun, but its aftereffects color their relationship, leading to their strained marriage when we are first introduced to them.

Jin is left behind on the freighter in season 4's finale, leading Sun (and audiences) to believe him dead. However, he survives and ends up bouncing through time to encounter a young Danielle Rousseau (Melissa Farman) in 1988, and joining other survivors during the formative years of the Dharma Initiative in 1974.

Trivia: Originally the only apparent survivor of the Oceanic 815 crash who does not speak English, Jin eventually learns the language during his three years with the Dharma Initiative.

12. Claire

Portrayed by: Emilie de Ravin

First Appearance: Pilot (Season 1, Episode 1)

Raised in Sydney, Australia, Claire Littleton survives the crash of Oceanic 815 roughly eight-months pregnant. While cared for by Charlie Pace and others, she is nonetheless abducted by the first of the Others the survivors encounter, a man named Ethan (William Mapother), for reasons later revealed to be tied to her pregnancy. This event proves to be so traumatic for her that she suffers from amnesia for a period of time, which drives a wedge between her and Charlie. Claire gives birth to her son, Aaron, on the island, with the aid of Kate, an event which is recalled in the final episode.

By the final season, she has become a hardened survivor left behind on the island, in a fashion similar to the older Danielle Rousseau (Mira Furlan), a stark contrast to the sweet, young girl from the beginning of the series.

Trivia: In the season 3 episode, “Par Avion,” it is revealed that Claire's father is Dr. Christian Shephard (John Terry), Jack's father, making Claire his sister.

11. Rose and Bernard

Portrayed by: L. Scott Caldwell (Rose) and Sam Anderson (Bernard)

First Appearance: Pilot (Season 1, Episode 1; Rose) and Adrift (Season 2, Episode 2; Bernard)

While Rose was one of the survivors of the midsection of the Oceanic 815—and thus part of the cast from the start—Bernard was only hinted at through the first season as perhaps being alive, or perhaps not, as he was in the tail section at the time of the crash. The fate of the “tailies” was not established until season 2, although Rose maintained that her husband was still alive even when presented with the possibility of it being otherwise by Jack.

Rose and Bernard compliment each other well, Rose being reserved but pragmatic, tempering Bernard's drive and overall enthusiasm. Rose was suffering from cancer prior to crashing on the island, but discovers that the island has healed her as it did Locke, a revelation which ultimately motivates their decision to build a life for themselves on the island independent of, as Rose describes it, the “drama” of the other survivors.

Trivia: The revelation in season 2 that Rose and Bernard were an interracial couple was also a surprise for the actors, just as it was for Hurley in “Collision,” another way the producers were able to subvert and reflect on audience expectations.

10. Jacob and the Man in Black

Portrayed by: Mark Pellegrino (Jacob) and Titus Welliver (Man in Black, real form)

First Appearance: The Incident (Season 5, Episodes 16+17; Jacob) and Pilot (Season 1, Episode 1; Man in Black, as “The Smoke Monster”)

Jacob and the (otherwise) unnamed Man in Black are the equivalent of gods, immortals and true residents of the island, keepers of its secrets and possessed of supernatural abilities beyond those of mortal men. Jacob is referenced as being the progenitor of the Others, a collective originally formed with the intention of guiding a “candidate” to inherit the island in Jacob's stead. The purpose of Jacob's stewardship over the island is to contain the malevolence that is the Man in Black, who harries and kills survivors of the island when they cannot otherwise be put toward his own goals. Jacob and the Man in Black knew each other as children, but became mortal enemies in a fashion similar to Cain and Abel. These two are at the crux of all the events that take place over the entire series.

Trivia: Jacob and the Man in Black were twin brothers born to a woman named Claudia, who was originally shipwrecked on the island at some point in the first century.

9. Ben

Portrayed by: Michael Emerson

First Appearance: One of Them (Season 2, Episode 14)

Originally introduced as Henry Gale to the survivors in season 2, Ben reveals himself to be the leader of the Others in the present, a group of residents on the island looking to both safeguard its power and acquire knowledge about its capabilities. Ben is portrayed through season 2 and 3 as the primary antagonist of the survivors, not above ruthless guile, deception, and even murder to achieve his ends. Ben's ultimate goal remains ambiguous throughout much of the series, and his allegiances shift dramatically, often changing the scope of the series' conflict with his actions. Raised on the island as a child under the Dharma Initiative, he believes that his actions will make him the successor of Jacob.

Trivia: In the “flash-sideways” storyline of season 6, Ben is portrayed as a history teacher, with a fascination for Napoleon Bonaparte, an ironic detail given Ben's own Napoleon complex.

8. Sawyer

Portrayed by: Josh Holloway

First Appearance: Pilot (Season 1, Episode 1)

Born James Ford, “Sawyer” is fundamentally the “anti-hero” of Lost. Originally portrayed as a cynical, sarcastic opportunist, Sawyer often agitates others to spur them into action. Sawyer's trademark is to give everyone nicknames—not unlike his own self-imposed alias—which is indicative of his reluctance to form relationships. Sawyer has a history of crime, primarily that of a confidence game, an element to his character which no doubt draws him and Kate closer together as the series progresses.

Sawyer's actions fluctuate dramatically from heroic to harsh, including leaping from an overloaded helicopter to save the other survivors when the opportunity for rescue comes, to shooting a member of the Others, Tom (M. C. Gainey), following his surrender out of vengeful spite; a true wild card.

Trivia: Sawyer and Locke share a common enemy from their past: Anthony Cooper (Kevin Tighe), who was Locke's father and the conman who went by the alias of “Tom Sawyer,” responsible for destroying Sawyer's family.

7. Ana Lucia

Portrayed by: Michelle Rodriguez

First Appearance: Exodus (Season 1, Episodes 23-25)

Ana Lucia Cortez assumes the mantle of the leader of the “tailies” following the crash of Oceanic 815. Unlike Jack or Locke, however, she lacks crucial skills of a successful leader, allowing her paranoia and insecurity effectively turn her into a tyrant, and cloud her otherwise sharp deductive acumen, honed by her former life as a police officer in the LAPD. Under her leadership, the tailies survival is a more harrowing experience, and is a stark contrast to the overall experience of the survivors of the midsection. She wears a tough exterior, but this is a hard shell to prevent the unresolved pain she feels at having lost her unborn child following a shooting in her former life.

Trivia: In the episode “Two for the Road,” Ana Lucia and Libby are both killed so suddenly that popular speculation was that as the actresses portraying these characters were both involved in encounters with the police on Hawaii (where Lost was filmed), that their characters were “written out” as a result.

6. Miles Straume

Portrayed by: Ken Leung

First Appearance: Confirmed Dead (Season 4, Episode 2)

Miles appears in the second half of the series as member of a group of specialists brought to the island by the freighter, The Kahana. He is a spirit medium, who can hear the thoughts of the dead, similar to Hurley's gift, and was recruited to come to the island to locate and obtain Ben Linus at the behest of his employer, Charles Widmore.

Miles' absentee father is revealed to be the lead researcher of the Dharma Initiative, Dr. Pierre Chang (François Chau), leading to interesting interactions when Miles is cast back in time into the formative years of the group. Over time, he develops a working relationship with Sawyer and banter back and forth, both in the past and the “flash-sideways” timeline in season 6.

Trivia: Many characters on Lost have names meant to reference famous philosophers, scientists, or mathematicians. Conversely, Miles' name was created to sound like “maelstrom,” because the producers thought “it was cool.”

5. Boone and Shannon

Portrayed by: Ian Somerhalder Boone) and Maggie Grace (Shannon)

First Appearance: Pilot (Season 1, Episode 1)

Step-siblings Boone Carlyle and Shannon Rutherford are initially two of the most unprepared for the realities of survival on the island following the crash of Oceanic 815. However, Boone desperately tries to contribute—even when he lacks the experience to do so—whereas Shannon actively avoids assisting in the efforts, a tack which Boone chastises her about. The “Flowers in the Attic”-style romantic tension between the two is expounded upon in the episode, “Hearts and Minds,” where Boone's “vision quest” initiated by his tutelage under Locke reveals the origins of Boone and Shannon and Boone's conflicted feelings for his stepsister.

Both were from affluent backgrounds, but Shannon's lifestyle and ability to continue to teach ballet hampered after her father's death. Boone and Shannon are some of the youngest survivors, and ironically the first to die on the island; Boone dies after injuries sustained while investigating a Beechcraft, and Shannon after being accidentally mistaken for an “Other” by Ana Lucia.

Trivia: The car crash which claims the life of Shannon's father is the same one which involved Jack's future wife, Sarah (Julie Bowen), depicted in “Man of Science, Man of Faith.” This means that Jack was in the unenviable position of having to choose Sarah over Shannon's father's life by chance.

4. Sayid

Portrayed by: Naveen Andrews

First Appearance: Pilot (Season 1, Episode 1)

SayidJarrah, like many of the survivors, hides an undesirable past from his fellows following the crash of Oceanic 815, which come out in short order in season 1. His past in the Iraqi Republican Guard left him with skills as an interrogator and torturer, skills which he reluctantly utilizes for the greater good of the survivors early on. A specialist and war veteran, Sayid is intelligent and resourceful, and often misunderstood by others who do not know him better.

Sayid develops a relationship with Shannon early on, although her death leaves him more embittered than before, and his subsequent torture of Henry Gale/Ben Linus reveals some dark truths to himself. Sayid occupies a unique role in a dramatic series as a complex major character for Lost, who also happens to be a Muslim in a post-9/11 era, upending audience expectations by virtue of his heroism and depth of character.

Trivia: Prior to his initiation as a torturer in Sayid's flashback in “One of Them,” he was an intelligence officer, whose skill with electronics helps the survivors inadvertently discover Danielle Rousseau's transmission, which had been broadcasting for sixteen years.

3. Juliet

Portrayed by: Elizabeth Mitchell

First Appearance: A Tale of Two Cities (Season 3, Episode 1)

Juliet makes her debut in the premiere of season 3, but her involvement with the Others goes deeper into the mythos. Although she is presented as an interrogator at first, her initial involvement with the others stems from her skills as a fertility doctor, brought to the island to find a resolution for a phenomenon which resulted in pregnant women dying.

Her flashbacks reveal a woman who was subdued and browbeaten by her manipulative ex-husband, but her tenure on the island has hardened her and molded her into becoming a strong-willed strategist and skilled player at the same kind of game played by Ben Linus, who harbors feelings for her. Originally portrayed as a potential love interest for Jack, after the island shifts in time, Juliet and Sawyer find themselves stranded in time, and begin a relationship instead.

Trivia: Juliet was brought to the island as a researcher in 2001 and lived among the Others for three years. After traveling back in time, she ends up living with the precursors of the Others—the Dharma Initiative—for yet another three years. Since her initial stay was one in which she was prevented from leaving, she is effectively stranded on the island twice as long as any other survivors.