Undertale

Flowey is the first key character encountered by the protagonist in Undertale. Flowey is the main antagonist in the Neutral Route and the True Pacifist Route, and can be considered the deuteragonist in the Genocide Route. Flowey introduces the player to the basics of gameplay by offering to increase their Joy Level (Joy Level) with "friendly petals," which are actually bullets he uses to launch attacks.
*Appearance:***Flowey is a golden flower with six petals, a white face, and a light green stem. Flowey can distort his face to imitate the facial expressions and voices of other characters. At times, he mimics Toriel and Asgore, and at the end of the Genocide Route, he mimics his previous self. He also mimics the protagonist's unchanging facial expression before the fight in the Neutral Route. *

• *Personality:***Flowey initially appears as a friendly and polite flower, but as the conversation progresses, he reveals his evil side, cursing at the protagonist, calling them an "idiot," and threatening to kill them, citing the principle of "kill or be killed." He is chased away by Toriel, but reappears at the end of Ruins, commenting on the protagonist's actions. As the game progresses, Flowey reveals his cruel side, mocking the protagonist for their pacifist actions and scolding them for ignoring the principle of "kill or be killed." He is a good planner when the situation demands it, and a skilled manipulator. He also possesses a wry sense of dark humor, which he demonstrates during his fight with himself at the end of the Neutral Route, trolling and ridiculing the protagonist. Despite his cruelty and evil actions, he nonetheless hints to the protagonist that he is, in some ways, their friend. As shown at the end of the True Pacifist's Route and the Genocide Route, he lacks a SOUL, and therefore the ability to show love and compassion. His malice may be an attempt to show any kind of emotion, even through disgust.

Toriel is a monster, the guardian of the Ruins, Asgore's ex-wife, and one of the key characters in Undertale. She is effectively the game's first boss, and is nearly impossible to die against.
*Appearance:***Toriel is a boss monster resembling an anthropomorphic Nubian goat with floppy ears and short horns. She has two visible fangs and long eyelashes, and the irises of her eyes are burgundy. Unlike real goats, Toriel has paws rather than hooves. She wears a purple robe with white sleeves and a Delta Rune symbol on the chest. She wears glasses when reading. *

• *Personality:***Toriel is a motherly monster who genuinely cares for the protagonist and their well-being. Despite her maternal traits, she also has a more serious side, which manifests itself in her attempts to keep the protagonist in the Ruins and her cold attitude toward Asgore. Toriel loves to cook and often uses snails as a main ingredient in her recipes, as her favorite dish is snail pie. She also enjoys baking butterscotch cinnamon pie. When Toriel was queen, she was considered an authoritative monster, although she claimed she always wanted to be a teacher. When the protagonist reached her home, she revealed that she had already prepared a plan for his education. In the True Pacifist ending's credits, she stands outside the school, and in the Neutral Route's family ending, she opens her own school in the Underground. It's unknown when exactly Toriel developed a love for bad jokes, but based on the contents of the first tape in the True Lab, it seems likely that it happened before Asriel was born. Despite her maternal nature, Toriel isn't above using swear words. Toby Fox, in a now-deleted tweet, claimed that Toriel can pronounce the F-word. According to Papyrus from Undertale Alarm Clock, Toriel once acted strangely after drinking too much eggnog; she sang holiday songs, replacing all words with curse words.

Sans is one of the key characters in Undertale and Papyrus's older brother. He is first encountered in the Snowdin forest, watching over the protagonist after they escape the Ruins. He serves as a supporting character in the Neutral Route and the True Pacifist Route, and is a heroic antagonist and final boss in the Genocide Route.
*Appearance:***Sans is a rather short and "big-boned" skeleton whose hands strongly resemble mittens. He is always seen with a wide, toothy grin on his face. Sans wears an unbuttoned blue jacket (or sweatshirt) with a gray hood and a white T-shirt underneath, black shorts with white stripes, and a pair of slippers. His black eye sockets contain white pupils that disappear when he is serious or angry. When using telekinesis, Sans's left eye iris flashes blue and yellow (the colors of patience and justice), while his right pupil disappears. *

• *Personality:***Sans has a very laid-back personality. He enjoys sleeping, which he does during his breaks at work. He's known for his jokes, which his brother, Papyrus, greatly dislikes. Sans is also kind and friendly. He believes in the good in others, and that they do bad things because something in their lives led to them. He believes that actions should be motivated by the desire to protect friends and help someone, not revenge. Sans once said that he doesn't like making promises, but when he does, he tries to keep them to the end. According to him, the only thing that saved the protagonist from death was his promise to Toriel to protect the fallen. On the Genocide Route, he can no longer keep this promise, but even as he contemplates breaking it to stop a mass murderer, Sans silently apologizes to Toriel. Sans is presented as a lazy character, but it is emphasized that this laziness is the result of his knowledge of timelines, and that everything he worked for can disappear without a trace with a single reset. Furthermore, Sans himself definitely doesn't consider

Papyrus is one of the key characters in Undertale and Sans's younger brother. He is the game's second boss and the boss of Snowdin, and is impossible to defeat. Completing the True Pacifist Path is impossible without befriending him.
*Appearance:***Papyrus is a tall, skeletal figure with an anatomically imprecise skull structure (compared to his brother's round skull). His mouth is almost always in a smile, and his pupil-less eyes resemble vertical slits, with expressions conveyed by his pseudo-eyebrows. Papyrus wears a homemade costume he made with Sans several weeks before the events of the game for a costume party, which he calls his "battle body." According to Sans, Papyrus wears it even when he showers. The costume consists of a white chest plate with gold accents, a short red cape, gold-accented gloves, blue shorts with a gold belt, and tall red boots. *

• *Personality:***Papyrus is a hot-tempered, loud, and charismatic skeleton who always strives to show off his best side. He works hard to gain recognition, and despite his demanding nature, he is kind and friendly to everyone. Papyrus is very optimistic and conscientious, demonstrated in the Genocide Route by his belief that the protagonist is good at heart, even if they attack and kill Papyrus. Papyrus truly believes in others, even more than he believes in himself. He is very persistent, a quality Undyne noticed when he waited outside her house all night to ask to join the Royal Guard. Undyne describes Papyrus as "drop dead strong," but also notes that he is too "innocent and good" for the Royal Guard. According to her, Undyne not only taught Papyrus cooking but also conducted daily combat training with him. Sometimes Papyrus is forgetful and inattentive, like when he tries out various MTT brand creams and sprays colognes behind his ears, only to realize later that he has no ears,

Undyne is one of the key characters in Undertale, encountered by the protagonist in Waterfall, where she resides. She is the head of the Royal Guard and is tasked with tracking humans. She is the third boss in the game and the boss of Waterfall. In the Genocide Route, Undyne transforms into Undyne the Undying after the protagonist fatally wounds her with a single blow. Undyne seeks to protect the monster race and defeat the protagonist.
*Appearance:***Undyne is a fish-like anthropomorphic monster. She has light blue scales and red hair tied in a ponytail, red and blue fins on the sides of her head, red spots on her eyelids, two protruding sharp yellow teeth, black vertical pupils, yellow sclera, and a black eyepatch over her left eye. Undyne lacks a nose. For most of the game, Undyne wears armor in Waterfall, with her hair likely acting as a plume. During the fight with the protagonist, she removes her helmet. At the party with the protagonist and in subsequent appearances, Undyne wears a black tank top, blue jeans, and red boots with yellow accents. Undyne's height is not precisely stated: in the open world, she is slightly shorter than Asgore, but at the end of the True Pacifist's Route, when all of the protagonist's friends gather before the final fight with Asriel, Undyne appears taller than Asgore. *

• *Character:***Undyne has a fiery and passionate personality. She quickly puts her ideas into action and is unwavering in her beliefs. Although she wants to kill the protagonist, she also tries to be fair and explains to them how SOUL's green mode works. Her training under Asgore taught her the value of pacifism, leading Undyne to view the protagonist as a "loser with a big heart." Undyne enjoys helping others and teaches Papyrus and Shyren various skills. She hates puzzles, loves jokes, enjoys playing the piano, collects weapons (primarily swords), and adores anime. This last interest stems from her romantic feelings for Alphys, as Alphys told Undyne that anime is the history of humanity.

Alphys is a reptilian monster. She is the royal court scientist, a position she earned by creating a robot with a SOUL—Mettaton. The protagonist first encounters her in the Hotland laboratory, which also serves as her home.
*Appearance:***Alphys is a yellow reptilian monster with protruding teeth (two to four, depending on which direction she's facing). She's the same height as the protagonist. Her posture is slightly hunched. She has three toes on each foot, and three normal fingers with a single thumb on each hand. Alphys wears only glasses (which don't cover her eyelashes) and a white lab coat. However, on her date with the protagonist, she wears a polka-dot dress that her friend helped her pick out. *

• *Personality:***Alphys is a shy, introverted woman who often stutters when speaking. She has low self-esteem, makes self-deprecating comments, and sometimes downplays her own skills. True to her role as a scientist, Alphys is intelligent, analytical, and observant. She sometimes theorizes on various subjects and can create meticulous plans based on them. She can create inventions using metal and magic, such as a "magic spear repair kit." Alphys is proficient in programming, robotics, and engineering. She is quick when working on projects and tries to maintain a formal, businesslike style when documenting her research.
  Alphys is very passionate about her work and interests. She often gets excited when sharing her opinions on various topics. Her hobbies include human anime, manga, and video games. Alphys enjoys posting online, writing game guides (though she prefers to offer puzzle solutions only as a last resort), shipping, and writing fanfiction. Alphys is attracted to both male and female characters. Some of these are mild, such as her crush on Asgore and complimenting Toriel.

Asgore Dreemurr (English: Asgore - the king of the entire Underground, Toriel's ex-husband, Asriel's father, adoptive father of the first fallen man)
*Appearance:***Asgore, like Toriel and Asriel, belongs to a special kind of monster—a boss monster. He is large, with golden hair and a beard, and long, spiraling horns on his head. He wears armor and a long purple cape with golden shoulder pads, giving the appearance of broad shoulders. His Delta Rune-shaped chestplate signifies his royal status. Asgore also wears a small crown with a gem inside (the gem is visible during the fight). *

• *Personality:***Asgore is introduced to the player as a calm, kind, and slightly confused family man, which is reflected in his dialogue with the protagonist during their meeting (Pacifist/Neutral playthrough). He tries to be good-natured, despite knowing the outcome of events. He presents himself as a warrior, but at the same time, killing brings him serious emotional distress. In his free time, he enjoys gardening and enjoys butterscotch pie and golden flower tea.
  Asgore has a habit of saying various words like: "Gosh" (Golly), "Howdy" (Howdy), which was later passed on to his son Asriel (and, concurrently, Flowey).
  Asgore is pretty bad at naming things (for example, he called the monsters' first home "Home," while he called the current capital of the Underground "New Home").
  The events that occurred before the game left a deep mark on Asgore's SOUL. During the game, he makes several difficult decisions that he morally disagrees with, but is forced to carry out. By the time the player begins the fight with him, Asgore realizes the terrible things he did to save his people, and he simply bows his head in shame during the battle.