Characters of Undertale and Deltarune

The Queen and King of the Underground in Undertale, they are members of a powerful, goat-like species called Boss Monsters. Asgore rules over the monster city of New Home. Toriel split from Asgore due to his desire to kill humans, collect their souls, and free the monsters by force, and now lives alone in the Ruins.

Toriel initially attempts to adopt the protagonist as her child. When the protagonist tries to escape, she is one of the game's first major bosses, attempting to prevent the player from entering the Underground and falling prey to Asgore. It is not made immediately obvious she can be spared, making her accidental death a common occurrence. The tendency of players to reload in an attempt to save her is one of the game's first demonstrations of Flowey's "meta" knowledge, as he will remember if the player has ever killed Toriel in the past. In the game's Toriel Ending, Toriel reclaims her position as Queen of the Underground and makes a rule where all humans will be treated as friends. This ending can play out in 3 different ways, with one being mentioned above.

The kindness of her character was seen by critics as a metaphor for the game's design as a whole. Jess Joho of Kill Screen called Toriel's "inhumanly selfless" behavior a common cliché of motherhood in popular culture, but described her as emblematic of Undertale's "maternal game design", since she teaches the player early on that they can show foes mercy. Joho noted that the tendency of players to kill Toriel out of impatience during their battle did not reflect the player's morality, but rather, how they were taught by "patriarchal" games that emphasized gaining power.[1] Nevertheless, some criticized the boss fight, with Julie Muncy of the same publication calling the process of sparing Toriel "incredibly counterintuitive", and saying that, despite not wanting to kill Toriel, the game marked her permanently as an aggressor for doing so.[2]

Asgore is encountered late into the game, and serves as the penultimate boss. Despite a fearsome reputation in battle, he is a kindly father figure in person, and is heavily reluctant to go through with his plan of destroying humanity. He is finished off by Flowey if the player attempts to show him mercy, but survives in the game's True Pacifist Route after Toriel's intervention.

In Deltarune, Toriel and Asgore are Kris' foster parents. Toriel is a teacher at a local school. Asgore remains divorced from Toriel, and runs a flower shop known as 'Flower King', referencing his Undertale incarnation's gardening hobby and being the King of the Underground.

In Undertale, Asriel is the now-deceased prince of the Underground, who was convinced by Chara, his adoptive human sibling, to participate in a plot to free the monsters, but later resisted. Asriel was then reincarnated as Flowey, but bereft of all empathy and compassion. In the game's True Pacifist Route, Flowey turns into an adult representation of Asriel, the "God of Hyperdeath" or ''Angel of Death'' . When defeated, Flowey returns to the form of child Asriel and regains his empathy.

Jason Schreier of Kotaku called Asriel's final boss fight one of the greatest in video game history, citing its climactic music and the necessity to save your friends from Asriel. Describing the sequence as "spectacular" and noting the emotion of the fight, he stated that, "if you’re not already bawling as you mash the SAVE button over and over again during the final part of this fight, well... you will".[3]

In Deltarune, Asriel is shown to exist, as Kris' brother, but has left for university.

Two skeleton brothers known for their outlandish human-capturing schemes. They function as comic relief within Undertale, their names each corresponding to a widely maligned typeface, Papyrus and Comic Sans, which they use for their dialog. Papyrus is egotistical yet incompetent, has a strong love for puzzles and spaghetti, who desperately wishes to join the Royal Guard, while Sans is a clever, laid-back slacker and trickster who often pulls practical jokes, and appears to sometimes break the fourth wall. Sans bonded with Toriel over their love of jokes. In the Genocide route Papyrus is shown to actually have a pure soul, always believing that the player can be good if they try.

In Undertale's Genocide route, Sans functions as the game's de facto final boss, revealing he is secretly an incredibly skilled fighter with control over the game's combat system, even breaking how battles work. While statistically weak, he uses a unique "Karma" mechanic to deal damage per frame and pure speed to dodge the player's attacks. The fight's theme music, Megalovania, became a widely renowned Internet meme. In the Papyrus Ending, Papyrus becomes leader of the Underground with Sans doing the work, however reveals that he is a bit nervous about the job as all the other main characters had been killed by the player unknown to him.

In Deltarune, Sans runs a grocery store known as "Sans", which outwardly resembles "Grillby's" from Undertale with the "Grillby" crossed out. When talking to Kris and Susie in Chapter 2, he refers to himself as its "janitor". Papyrus is not seen, but implied to exist as Sans mentions having a brother, alongside some dialogue referring to Papyrus' main battle theme 'Bonetrousle'.

In Undertale, Undyne is the immensely powerful leader of Asgore's Royal Guard and leader of the Underground (Undyne Ending or alternate Toriel Ending). She is largely humanoid, but with fish-like features. While initially presented as an intimidating figure, her ham-fisted behavior in combat is heavily inspired by anime, which she falsely believes to be an accurate representation of the human world. Undyne possesses a small amount of Determination, a substance that makes humans far stronger than monsters, that enables her to resurrect once upon death. It is theorized this is due to the intervention of her love interest, Alphys, who was conducting experiments on injecting Determination into monsters.[4]

In Deltarune, she is the town's police officer after Asgore was fired.

In Undertale, Alphys is Asgore's Royal Scientist, or the leader of the Underground (Alphys Ending). She is a shy, nerdy, lizard-like woman who is a heavy otaku. She created Mettaton's robot body, at the cost of abandoning his cousin Napstablook. She tries to earn the protagonist's trust by helping them fight off Mettaton throughout Hotland, but Mettaton reveals he was simply acting to make Alphys seem better. She is the successor of W. D. Gaster, who served as Royal Scientist until he was shattered across time and space by one of his creations. She commonly demotivates herself and considers herself inferior, and is hinted to commit suicide depending on the actions of the player in game.

In Deltarune, she is another teacher at Kris' school, and is quite nervous around Susie.

In Undertale, Mettaton is a robotic entertainer who is the Underground's premier celebrity, the leader of the Underground (Mettaton Ending) or is providing various television shows, product brands, and a hotel in Hotland. An egotistical glory-seeker, he wants to take a human soul to travel to the surface and become a celebrity amongst the humans, and tricks Alphys into helping the protagonist to reach the CORE so he can kill them. It is revealed through diaries in an abandoned house that Mettaton was originally a ghost who dreamed of creating a perfect body for themselves, and got their chance when they befriended Alphys at the cost of abandoning their cousin Napstablook. In the Genocide Route, Mettaton becomes his NEO form, but can be killed by the player in 1 hit. In the True Pacifist Route, he is reunited with Napstablook, who becomes his sound mixer.

In Deltarune, while Mettaton is not seen, they are almost certainly the ghost behind the door of Napstablook's house.

In Undertale, Napstablook is Mettaton's cousin, an introverted ghost and DJ. The protagonist battles them in the first area of the game, and can befriend them later at their house in the third area.

In Deltarune, they work as a police officer with Undyne, but do not notice that all of the town's criminals have escaped until the protagonist talks to them.

A child from the Surface and the main playable character of Undertale, they are initially presented as a player-nameable character also known as the "fallen human". In a late-game plot twist exclusive to the True Pacifist Route, it is revealed that the "fallen human" only superficially resembled Frisk, but had arrived years earlier. Frisk has an androgynous appearance, and is a silent protagonist, leaving their gender and personality for the player to decide. They spend the game searching for a means to escape the Underground.

A child from the human world known as the "fallen human", their default name is Chara, but they are nameable by the player. They are hinted as having climbed Mount Ebott to escape humanity, and, despite having been taken in by the monsters as a foster child, attempted to enact a plan to destroy humanity and free the monsters by fusing their soul with their foster brother, Asriel. It fails, leading to their death and later burial in the Ruins. In the game's Genocide route, Chara is resurrected as a soulless and demonic being who seeks to erase the world. There have been theories in the Deltarune community that Chara is in Deltarune, but they have yet to make an appearance.

Flowey is a flower who initially pretends to be kind-hearted, but has a sociopathic personality and the ability to operate outside the laws of the universe. A powerful, eldritch version of him known as Photoshop Flowey or Omega Flowey serves as the final boss of the game's Neutral route. Flowey is later revealed to be the reincarnation of Asriel Dreemurr, the deceased prince of the Underground.

The former Royal Scientist before Alphys, Gaster was purported to have been "shattered across time and space" after accidentally falling into one of his creations, likely the Underground's geothermal power station, the CORE. He only exists as Easter eggs within the game. Also known as "the man who speaks in hands", his initials refer to the dingbat font Wingdings in a similar manner to Papyrus and Sans. Though he has no clear canonical appearance, fans generally believe he is a warped sprite known as the "Mystery Man", although some believe it to be another sprite nicknamed "Redacted". A mysterious voice and other clues hint at Gaster also being involved in the events of Deltarune mainly through The Man Behind The Tree and the aforementioned Voice, but his presence has yet to be explicitly confirmed.[5]

Mad Dummy is a character located in waterfall presumed to Napstablook's cousin and therefore Mettatons's cousin. Mad Dummy is a ghost that has possessed a dummy which attacks you as a mini-boss just before quiet area.

In the Genocide Route Mad Dummy becomes Glad Dummy because the ghost's spirit is fully "merged" with the dummy.

An androgynous, introverted teenage human who was adopted by Toriel and functions as the player character of the game. They are stated to have a trickster personality, which other characters note the absence of during the player's influence. They are able to remove their soul from their body and exercise free will outside of the player's control, implying it is not their own soul. At the end of Chapter 2, Kris is shown to create a Dark Fountain when not controlled by the player.

A mysterious entity that typically controls Kris through a red soul, though it can jump to other characters if necessary. When Kris removes their soul, representing the player, they throw it in a birdcage. In the secret SnowGrave route, the player manipulates Kris into forcing Noelle to freeze Berdly and many Darkners solid.

Lancer is the miniboss of Chapter 1, but also appears in Chapter 2 of the game. He is the son of King, the final boss of Chapter 1. He is energetic yet incompotent in his attempts to stop the heroes to earn his father's respect.

King is the final boss of Chapter 1, and is the father of Lancer. He is the antagonist of Chapter 1, and is shown to be a tyrannical figure with little care for his subjects or family. He has a rotund body and a second mouth on his stomach with a spade sticking out of it. He is also sometimes known as ''Chaos King'' or "King of Spades".

Queen is the main antagonist and final boss of Chapter 2. She is a robot, and attempts to capture the party multiple times, although she has no ill will towards them and is mostly a friendly if eccentric figure. She has another name, known as "Serial Number Q5U4EX7YY2E9N". She is Lancer's adoptive mother, although whether she is his biological mother is unclear.

The prince of the Dark World, he wears a green robe and wizard-like hat that covers him entirely in shadow in Chapter 1. He tells Kris of the threat posed by the Dark Fountains, and appears to be meek and kind-hearted, encouraging the player to deal with enemies in a non-violent way. When the hat is removed, he is revealed to look similar to Asriel, in addition to their names being anagrams.

A purple, alligator-like fellow student with great strength, and a gruff, tomboyish appearance and demeanor. She uses an axe, and becomes one of the player's main party members. She starts out aggressive and unwilling to use mercy or befriend people, but mellows out over the course of Chapter 1 and becomes more friendly if boisterous in Chapter 2.

A dainty fellow student resembling an anthropomorphic reindeer, she joins the player's party in Chapter 2. In the Dark World, she wears a white robe and has proficiency for magic. The player is able to use her "IceShock" spell to freeze enemies solid, and, if a certain sequence of events is followed, prompt a darker secret route in which Berdly is trapped in ice with the "SnowGrave" spell. Her father also reveals that she has a crush on Susie.

A know-it-all student who becomes Kris's rival in Chapter 2, and later becomes their ally. It is revealed that Noelle is actually smarter than him, but he has continued his snobbish persona in order to gain attention and praise. If frozen solid in the SnowGrave route, he does not reawaken in the real world.

A Darkner who is a personified Joker card optionally encountered in Chapter 1. He was locked away after an interaction with a strange unknown figure, implied to be W.D. Gaster, drove him to madness. He began to see his whole world as merely a game and all it's inhabitants merely parts of the game. Despite being locked in a cell, he now believes all the other inhabitants of the Dark World have imprisoned themselves and he is the only free Darkner remaining. Upon being set free, he challenges the party to a battle as a "game" and serves as the superboss of Chapter 1.

A personified spambot Darkner with a marionette-like appearance encountered in Chapter 2, he speaks in mangled, cryptic English peppered with bracketed marketing keywords in the manner of a spam email. Spamton has the personality of a used car salesman, and is obsessed with becoming a "BIG SHOT". He plays a role in unlocking the chapter's hidden route by selling the player the Thorn Ring, and also functions as that chapter's superboss, Spamton NEO, after merging with a defunct robotic body resembling Mettaton NEO; he is also capable of accessing this form in the normal route by performing certain actions in his shop and in Queen's Mansion. He is the secret boss of the normal route and the final boss of Chapter 2's hidden route. Upon defeating him in the normal route, the player can revisit his shop and speak with his former coworkers, who explain how he rose to success after making a Faustian bargain with an anonymous voice on the phone, only to lose his job, home, and sanity when the figure abandoned him. His name is an anagram of Postman, which ties in to his spam mail personality.