Frisk is the playable character and main protagonist of Undertale. After Frisk falls into the Underground, they embark on a journey to return to the surface, whether peacefully, neutrally or genocidally.
Frisk's name is only revealed in the True Pacifist Route, confirming that they're not the "fallen human" whom the player names at the beginning of the game.
Frisk is a yellow-skinned human child who wears a blue long-sleeved shirt with two purple colored stripes on its center, blue pants (often depicted as shorts in the official Undertale merch), and brown shoes (usually depicted as black or in a darker tone).
They have medium-length straight brown hair, short and choppy bangs, and a blank expression. Though Frisk does not show much expression in the overworld, NPCs often describe Frisk's expressions.
Just like the first human, they have no stated gender and are solely referred to as "they/them" pronouns throughout the game, or by generic terms (such as "child", "human" or "kid).
Frisk's personality is usually ambiguous, allowing the player to project any personality onto Frisk since they're very often speechless to them. However, the narration that describes Frisk's actions occasionally changes depending on their LOVE.
Frisk speaks to NPCs throughout the game, especially when ACTing in encounters, but the exact dialogue is shown only when the game gives multiple dialogue options. NPCs' dialogue boxes display "..." to show that the NPC is listening to Frisk, and some NPCs respond to questions that Frisk asks.
Depending on their actions, players can interpret Frisk as merciful and kind, or merciless and violent. Some NPCs emphasize Frisk's kindness, understanding, and grace in the epilogue.
Frisk is obedient and only disallows player input when they follow someone else's instructions, such as when Sans tells them to hide behind the conveniently-shaped lamp.
Frisk's determination grants the power to SAVE, heal at SAVE Points, and respawn at SAVE Points after death. This power emerged when Frisk first awoke in the Ruins.
Frisk can reload the SAVE file to repeat events that occur after it, but NPCs' memories are not completely erased unless a True Reset occurs. After the True Pacifist ending, Flowey's dialogue implies that Frisk is not the being who is manipulating SAVE files.
Frisk is the only character who is ever shown using items or gaining EXP.
Chara , also known as the fallen human, is the first human to fall into the Underground.
Chara is their "true name" on the naming screen, though their name typically varies on what the player enters.
They are distinct from the eighth fallen human, who is the protagonist of Undertale.
Their primary role is in the backstory of the Dreemurr family, though they also appear at the end of the Genocide Route to erase the world.
Both of these make them a major character in Undertale.
Chara looks strikingly similar to the protagonist. They both have an ambiguous gender, and a "similar fashion choice," as said by Asriel Dreemurr in the True Pacifist Route.
Both appear to have been around the same age when they fell into the Underground. Chara's SOUL is also the same color as the protagonist's, which is indicated by the red SOUL on Chara's coffin, but any other shared traits are unknown.
At the end of the Genocide Route, Chara is seen to be wearing a lime and cream-colored striped shirt (which is an inverted color of the protagonist's shirt, with a single stripe) and red-brown pants and shoes.
Chara has peach skin and brown hair, rosy cheeks, open brown eyes, and a smile that contrasts the protagonist's stoic expression. In the "Soulless Pacifist" ending, Chara appears with red eyes.
While initially cast in a sympathetic light, Asriel admits at the end of the True Pacifist Route that Chara "...wasn't really the greatest person." Asriel states that Chara climbed Mount Ebott for an unhappy reason, and adds that Chara "hated humanity."
At the end of the Genocide Route, Chara behaves in a polite, formal, and terse manner. They thank the protagonist for teaching them the purpose of their reawakening: power. Chara informs that their determination woke them from death when entering the Underground.
If the protagonist refuses to destroy the world, Chara's eyes become wide, and rhetorically asks: "SINCE WHEN WERE YOU THE ONE IN CONTROL?", before destroying it with corrupt laughter. In the abyss, Chara is blunt, and criticizes the protagonist: "You want to go back to the world you destroyed."
After a second Genocide Route, Chara expresses confusion at the protagonist's "sentimentality," and states that they can no longer understand such emotions, implying that they, like Flowey, have lacked a SOUL, and thus emotions, since their death.
Flowey is the first major character that the protagonist encounters in Undertale. Flowey serves as the main antagonist for the Neutral and True Pacifist routes, and can be considered a deuteragonist for the Genocide Route.
He provides an introduction to the mechanics of encounters by sharing "friendliness pellets," which are actually harmful bullets, revealing his philosophy of "KILL or BE KILLED." He serves as the final boss of the Neutral Route.
Flowey has the appearance of a conscious golden flower. His structure has a white androecium, six yellow petals, and a light-green stem. Flowey can contort his face to show various expressions and can mimic the faces and voices of other characters.
He mimics Toriel and Asgore in some situations, as well as his old self at the end of the Genocide Route. He also mimics the protagonist's face before the Neutral Route's final battle.
Toriel is a goat-like monster who is the second major character the protagonist encounters in Undertale.
She saves the protagonist from Flowey and guides them through the Ruins, of which she is the self-proclaimed caretaker.
She is the ex-wife of Asgore, the mother of Asriel Dreemurr, the adoptive mother of the first human, and the first boss, guarding the end of the Ruins.
She tries to protect the human from the dangers in the Underground, providing a safe tutorial through the first few rooms of the game.
Toriel is a Boss Monster whose head resembles a white-furred Nubian Goat, structured with floppy ears and tiny horns. She has a pair of visible fangs and long eyelashes, and her irises have a dark red tint.
She has an anthropomorphic body, with paws at the end of her limbs. She wears a long purple robe with white sleeves and the Delta Rune on the chest. Toriel can also be seen with reading glasses, one instance being in her house when reading a book on snail facts.
Papyrus is the brother of Sans and a major character in Undertale. His main motive is to capture a human so he can become a member of the Royal Guard, and finally have friends and popularity. He serves as the final boss of Snowdin.
Papyrus is a tall, perhaps anatomically inaccurate skeleton, with a skull more vertical and geometric than his brother.
Being skeletal, many of his expressions incorporate a toothy grin. His eyes resemble vertical slits; his skeletal pseudo-brows form most of his expressions, as well as the corners of his mouth. He has eyeballs which show at times when he is experiencing strong emotions.
Papyrus is relatively taller and slightly slimmer than his brother.
Papyrus is a flamboyant skeleton who presents a confident, charismatic image of himself. He is thought to have an egotistical personality, referring to himself as "THE GREAT PAPYRUS," possibly as a way to feel as prestigious as his brother. He works hard and, despite his brash personality, is kind at heart.
He is optimistic and brave, and is shown to be considerate and forgiving even when the protagonist beheads him in the Genocide Route. He is also occasionally oblivious and nonobservant, but can be cunning at times, as seen when he uses reverse psychology to trick Undyne into befriending the protagonist.
He is thought of to be somewhat naive by other characters, but not dumb. He shows great bravery as even in the face of potentially imminent death, he drops his guard and spares the protagonist hopes of driving them down a better path.
Undyne , known as StrongFish91 on the UnderNet, is a fish-like monster that leads the Royal Guard. Considered a heroine of the Underground, she pursues the protagonist through the entirety of Waterfall
And is frequently evaded or inadvertently thwarted by Monster Kid. She serves as the main boss of Waterfall and a major character in Undertale.
Undyne is a piscine, anthropomorphic monster. She has blue scales and a long red ponytail. She has red and blue fins on the sides of her head, and a pair of sharp, yellow, protruding teeth.
She wears a red eyeshadow and has an eyepatch over her left eye. She also wears a black tank top and blue jeans, but debuts in armor varying in light and dark shades of gray.
Her eyes have black vertical pupils and yellow sclera. Undyne has no nose.
Dr. Alphys is a female, reptilian monster that lives in the lab in western Hotland. She is the incumbent Royal Scientist, a position she was awarded by Asgore after the disappearance of her predecessor. She is a major character in Undertale and the only one not to fight the protagonist.
Alphys is a yellow, reptilian monster of similar height to the protagonist. Her posture is somewhat hunched over. She has yellow scales, claws, and protruding teeth (which seem to vary between two and four depending which way she faces). Her feet have three toes while there are three fingers and a thumb on each of her hands. Her "hair" is designed into points facing the back of her head.
She normally wears round glasses and a white lab coat. Her glasses do not cover her eyelashes. However, she wears a polka dot dress a friend picked for her on her date with the protagonist.
Alphys is a shy introvert who frequently stutters when she converses. She has low self-esteem, makes self-deprecating comments, and devalues her skills at times. True to her role as a scientist, Alphys is intelligent, analytical, and observant.
She occasionally theorizes on matters, and can create thorough plans from them. She can create inventions that use metal and magic, such as a "magical spear repair kit." Alphys is adept in programming, robotic, and mechanical engineering.
She is agile when she works a project,[12] and has formal writing when documenting her research.
Mettaton is a robot with a SOUL and was built by Alphys. Initially poised as an entertainment robot turned human killing robot, Mettaton is later revealed to have only acted as such so that Alphys could rescue the protagonist, feel important and become closer to them.
Mettaton is the sole television star of the Underground. He serves as the final boss of the CORE and a major character in Undertale.
Initial Form Mettaton originally appears as a gray, largely rectangular box with a 4x5 grid of rectangular lights at the top, similar to the mechanism in Snowdin Forest used for Papyrus's Tile Puzzle. The grid of lights can change colors between red, yellow, green, and blue, and Mettaton uses these color changes in place of facial expressions
He has four dials along the bottom of his body, and the bottom, he has a single leg which ends in a wheel. He has two segmented robotic arms which end in white gloves.
Mettaton EX After having the switch on his back flipped in the Neutral or True Pacifist Route, Mettaton transforms into Mettaton EX; a new body he specially requested Alphys make for him. In this humanoid form, he has black hair with a long fringe that seems to cover his right eye, pale "skin" and visible metal segments below and above his left eye.
He has a pink chest piece, a narrow metallic waist with a box contraption, and black shoulder pads above his segmented arms, which end in gloves.
The chest piece has what appear to be a speaker and some knob or gauge, while the waist has two parts that seem to act as a locking mechanism that holds his "heart-shaped core," as they both lose white pixels during his "heart-to-heart" attack. His long black-clad legs end in pink high-heeled boots.
Mettaton NEO After being confronted by the protagonist on the Genocide Route, Mettaton transforms into Mettaton NEO, which resembles Mettaton EX, but has a more combat-oriented design, however Mettaton NEO can be killed by a single attack and has no attacks of his own.
His right forearm is replaced by what appears to be a cannon, pauldrons clad his shoulders, which are shaped like legs and are longer than his arms, and he has wings on his back. The soul on his waist points upwards in a more monster-like manner, and he has a heart shape engraved on his chest plate like Undyne the Undying, also mimicking the Delta Rune in the same ways. His hair on the right side is spiked out, revealing an entirely black segment of his face, with a sparkle or crosshair in place of his right eye.
Mettaton is a confident, charismatic, and charming TV host that loves drama, action, and violence. He lives for his ratings and adores performing. He supposedly strikes a pose when he does something wrong and makes time on his variou shows to beat up "heel-turning villains." He shows a rather shallow appreciation for existence at times.
He has a strong craving for attention and is very egotistical for the point of narcissism, such as boasting about the beauty of his true form. However, despite his seemingly narcissistic personality, he deeply cares about the seemingly positive impact his show has had on the inhabitants of the Underground. He has also shown soft spots for several characters, such as Alphys and Napstablook.
Asgore Dreemurr is the ruler of the Underground and its denizens, monsters. He is the ex-husband of Toriel, father of Asriel Dreemurr, adoptive father of the first human, and the penultimate boss of the Neutral Route. While not evil or malicious, he serves as one of the main antagonists of Undertale, planning to kill seven humans and use their SOULs to break the barrier which traps the monsters in the Underground.
Asgore is a Boss Monster with an intimidating stature. He has broad shoulders, a golden-blond mane, two large curved horns, and a beard. He wears a suit of armor, a purple cape with golden pauldrons - with its edge dragging along the ground slightly - and a small crown on top of his head. The weapon he uses in battle is a long, red trident adorned with a flower.
Asgore is shown to be the largest main character (whether human or monster) in the entire game. Towards the end of the game, Asgore appears to be more fat with a large gut rather than the broad-chested Herculean build he portrays: albeit he keeps his wide bulky appearance, his tall stature and especially his overall muscular limbs.
This trick of appearance where Asgore seems more fit than he actually is likely fits into a common trope of fat characters sucking in their guts as an effort to look more intimidating, Asgore doing something similar by encasing himself in tight likely uncomfortable armor. However, after the True Pacifist Route he wears what looks to be a far more comfortable Hawaiian T-shirt which is pink in color and has white flowers alongside a simple pair of blue jeans.
His arms are also shown to have stripes of yellow fur on top of them seemingly replicating the look of body hair.
Asgore is a kind and often quiet yet upbeat monster that enjoys gardening, Golden Flower Tea, and Toriel's Butterscotch Pie. Like his son, he speaks in southern slang (most notably "howdy" and "golly"). Before his battle, he offers the protagonist many opportunities to explore the Underground and is reluctant to fight them at all; he even suggests that Toriel, the protagonist and himself live as a family if the protagonist spares him.
Asriel Dreemurr is the biological child of Toriel and Asgore and the adoptive brother of the first human. He serves as the final boss of the True Pacifist Route, replacing Asgore in New Home. Despite his late introduction, his presence as Flowey as well as in the game's backstory makes him a major character.
Like Toriel and Asgore, Asriel is a Boss Monster with white fur, long ears, a snout, and a set of visible fangs. In his child form, he lacks horns and has a small tuft of fur atop his head, unlike his parents. He wears a green long-sleeved shirt with yellow stripes and black pants, similar to the first human's clothing.
Before his death, Asriel was a docile, unadventurous, and loving child. He cared for the first human as a sibling, and he trusted them when they came up with a plan to escape the Underground that involved the human consuming buttercups.
After Alphys resurrects Asriel without a SOUL as Flowey, he becomes incapable of feeling love. This makes him grow bored and resentful.
After temporarily regaining his compassion, he apologizes for his actions to Frisk and realizes the gravity of his actions as a flower. Much like his father, Asgore, he commonly speaks southern U.S. slang.
Sans is the brother of Papyrus and a major character in Undertale. He first appears in Snowdin Forest after the protagonist exits the Ruins. He is the deuteragonist of Neutral and True Pacifist routes keeping an eye on the protagonist, and as the final boss and heroic antagonist in the Genocide Route trying to stop a human in the last corridor.
Sans appears as a relatively short and paunchy skeleton, with mitten-like hands. Sans is always seen with a wide, toothy-grin on his face. Sans wears a blue hoodie, a white t-shirt underneath, black shorts with white stripes, and a pair of slippers
He has white dots in black eye sockets that disappear when he is serious or angered. When Sans uses telekinesis, his left eye flashes light blue and yellow (the colors for patience and justice) while his right pupil vanishes.
Sans is lazy, often sleeping on the job and taking breaks. His laziness is a combination of fatalism and apathy, as he is aware of timeline resets. Conversely, he suggests that this knowledge could be "a poor excuse for being lazy."
He enjoys being mischievous. Sans primarily acts this way towards those he is in good terms with. His antics range from an assortment of illogical, juvenile, and slightly inconvenient pranks. Examples include Sans "selling fried snow," using whoopee cushions, sharing an unscrewed ketchup bottle, and eye paint on a telescope.
He is not above utilizing his teleportation or other magic for practical jokes either. Sans is also fond of making the occasional low-brow puns. He enjoys making others laugh in general, as he also performs at the MTT Resort as a comedian.
Despite Sans being apathetic towards his own life, he is considerate to those he cares for. For example, Sans is a regular at Grillby's, and the monsters and Royal Guard dogs treat him kindly. Sans has informed Big Mouth about "all kinds of incredible foods," yet Big Mouth comments that "he always orders the worst burger off the menu." Although Sans hates making promises, he respects Toriel's request to watch out for any humans. Even if the protagonist killed people that were close to him, Sans refrains from broaching the topic until the Last Corridor. In a Neutral Route ending where Papyrus or Toriel is alive, Sans omits the protagonist's slaughter to either of them.
He is also observant; Sans reads the protagonist's expressions and can often tell when they have already done certain tasks. Though Sans is usually agreeable, he can become eerily serious to emphasize a subject. Regardless of the human being partially or wholly merciful, Sans tells them that if "the old lady" had not made him promise to protect them, "(they'd) be dead where (they) stand." During the Genocide Route, he does everything in his power to kill the protagonist, even faking mercy.
Sans may have a scientific background. Evidence includes the quantum physics book, his workshop, affinity for science, his inexplicable ability to teleport and his timeline research.
Sans has implied he once longed and searched for a life that he cannot go back to as he "gave up trying to go back a long time ago". As a Lost Soul, he tells the protagonist that "you'll never see 'em again." Although what Sans is trying to return to is vague.