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Yo... Y-you'd b-better st-stop r-right where you are... Cause if you w-wanna hurt anyone else... you're... You' re gonna have to get through me, first. A... and... and...
~ Monster Kid to the protagonist in Genocide Route.
Undyne... You.... You saved me! Huh? They ran away? Yo, you're wrong... They went to get help! They'll be back any second!!
~ Monster Kid to Undyne if the protagonist decides to run away in Neutral Route.

Monster Kid is a character in the indie game Undertale, released in 2015. They are a monster who lives in Underground with the other monsters. They act as the supporting character in Neutral and True Pacifist Routes, and as the heroic antagonist in Genocide Route.


Monster Kid is a yellow, reptilian kid monster with no arms, spikes on the back of their head and a tail. They have brown markings under their black eyes. They wear a yellow shirt with brown stripes and brown shoes.


Monster Kid is a notably weak monster, and one might assume that their lack of arms contributes to that. Getting to know Monster Kid better, though, it becomes abundantly clear that they are incredibly strong willed and make up for their disability with intense bravery and perseverance. They idolize those they view as strong, wishing to become a hero one day to protect some of the more helpless monsters in the Underground.



Monster Kid has 2 ATK and 2 DEF, nearly the lowest in the entire game. They will not attack the protagonist in their battle, however, and will quiver anxiously and attempt to diffuse the situation with words rather than violence. This battle can end in two ways. The first is the resolution that will push you into the Neutral Route. This happens when you spare Monster Kid. They will remark that you may not be as evil as you seem, before fleeing. This aborts any progress on the Genocide Route. The next is the resolution that will continue the Genocide Route. By attacking Monster Kid, Undyne will intervene and take the hit. This hit is strong enough to instantly kill her, thus reviving her as Undyne the Undying. Monster Kid flees, and presumably evacuates with Alphys.

Neutral Route

When the protagonist first meets Monster Kid, they bond over both wearing striped sweaters. They don't realize that the protagonist is a human.

A while after, the protagonist encounters Monster Kid in Waterfall, where Monster Kid explains that they are hiding to try to catch a glimpse at Undyne, explaining their idolization of her. Later, when the two are walking, they encounter Undyne. Monster Kid seems to be jealous that Undyne acknowledged the human, unaware of why she acknowledged them in the first place.

When the protagonist is walking with Monster Kid again, they marvel at the beautiful sights at the Underground, before the two encounter an impassable wall. Monster Kid then has an idea, offering for the protagonist to use their head as a stepping stool. The protagonist utilizes Monster Kid to pass the wall.

Later, on the bridge, Monster Kid appears to question the protagonist about what Undyne taught them. They claim that, according to Undyne, Monster Kid and the protagonist ought to be enemies, since the protagonist is a human. Monster Kid has doubts about what Undyne taught them, though, desperately trying to retain a friendship with the protagonist. They walk away, dejected.

When they are leaving, they fall and trip over the edge, dangling for their life. The protagonist has four choices:

  • Save them: If the protagonist helps Monster Kid climb back up, Monster Kid will defend the protagonist from Undyne and they will remain friends.
  • Let them fall: If the protagonist lets Monster Kid fall, Undyne will dive down after Monster Kid to save them. Monster Kid severs their friendship with the protagonist.
  • Run to Undyne: If the protagonist runs to Undyne, Undyne will ignore them and dash to save Monster Kid. This also causes Monster Kid to sever their friendship with the protagonist.
  • Run away from Undyne: If the protagonist runs away from Undyne, she will again save Monster Kid, who assumes that they had ran away to get help.

True Pacifist

Monster Kid is seen cheering the protagonist on to victory along with other monsters during the Asriel Dreemurr fight.

In the epilogue, if the protagonist talks to Monster Kid, they will remark that they're over their obsession with Undyne, and that they've found a new idol, Papyrus. If Undyne has to intervene to save Monster Kid, they will not talk to the protagonist afterwards.

In the end credits, they are seen attending Toriel's school.

Genocide Route

Monster Kid's role is identical to that in the Neutral Route, although in this Route, Monster Kid will stand up against the protagonist. They nearly risk their life, and when the protagonist attempts to attack, Undyne will intervene and take the hit. Undyne then dies, and is revived as Undyne the Undying. She instructs Monster Kid to escape.


  • In the Japanese translation, Monster Kid uses "ore" for themself, which is commonly used for males.
    • Monster Kid is referred to as a male in the Art Book, however this is likely an error, as Napstablook was also erroneously referred to as male before it was changed.


           Undertale Logo.jpg /Deltarune Logo.png Heroes

Frisk | Papyrus | Sans | Toriel | Alphys | Undyne | Mettaton | Asgore Dreemurr | Asriel Dreemurr | Monster Kid | Muffet
Kris | Susie | Ralsei | Lancer | Rouxls Kaard | Seam

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