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This article, Koi, is owned by WinterCatzuli. Please do not edit this article without their explicit permission.

NOTE: This page is still a WIP. More content should be added soon! Additionally, this is my first wiki page. Constructive criticism would be appreciated!

Koi is a member of the species known as Catfish, who's name is quite literal regarding appearance. Of course, they aren't literal hybrids, rather a subspecies of monster. They are clad in many fur and scale colours, the latter often ranging from greys, greens, oranges, reds, and blues with the occasional yellow tail, the former with any coat colour of a normal cat possible.


This catfish in particular is orange-furred, with aqua blue scales lining the spinal fin, tail, back, and paws with a few scattered elsewhere. A cream patch of fur forms a ring around their left eye, similar cream patches of fur sprouting out from between the scales at the base of the tail. Translucent flaps of skin line the area between the dorsal fins, forming one large sail-like spinal fin. Catlike fangs adorn the face, which sits below two black, rounded, fishlike eyes. Unlike their fish counterparts, however, they do not bulge out of the head, rather set in the skull like those of a cat. Like every other member of the species, Koi can breathe through both lungs and the gills they possess, though they get winded on land fairly quickly.

Stats and ACTs

Base Stats

AT: 8

DF: 2

HP: 90


Check, Splash, Taunt, Pet

In Battle


Koi has a total of two different attacks:

  • The first is simply a paw swiping across the top or bottom of the bullet board respectively. When taunted, the paw moves more slowly across the board, making damage easier to avoid.
  • The second attack is a droplet-like projectile that falls to the bottom of the bullet board, resulting in a spray of other (much smaller) water droplet projectiles. They will start to curve towards the soul, though not to an unavoidable degree. Taunting has no effect on this attack.


In order to spare them, they must be splashed at least once then pet at least once.


"..." [Neutral]

"Hello...?" [Neutral]

"Too... close." [Pet before Splash]

"Way... too... close." [Pet #3+ before Splash]

"Why... thank you." [Splash #1]

"Wow... thanks!" [Splash #2-3]

"I cannot thank you enough!" [Splash #4]

"Haha!" [Splash #5+]

"Purrrr..." [Pet after Splash, can now be spared]

"Purrrr... zzZZZ" [Pet #2+ after Splash, can still be spared, attacks will cease]

"H-Hey!" [Taunt]

"Me-ouch!" [Non-fatal attack]

Flavour Text

Koi pads up curiously [Encounter]

Koi sniffs the air cautiously [Neutral]

Smells like wet... cat? [Neutral]

Koi is bouncing a globule of water off of their tail, seemingly for no reason at all. [Neutral]

Seems to have an affinity for water, despite appearing like a cat. [Check]

You reach out to pat them on the head. It seems to shy away from your touch. [Pet #1 before splash]

You try to pet it again. It shies away further. [Pet #2 before Splash]

You barely lifted your hand and Koi has already hidden in a clump of nearby reeds. [Pet #3+ before Splash]

You feebly spray the catfish with a few drops of water. It looks... happy? [Splash #1]

You splash with both hands this time, its smile grows wider. [Splash #2-3]

Koi is running out of ways to thank you, it's so grateful. [Splash #4]

Well, Koi is now soaked to the bone, but looks happier than ever. [Splash #5]

Any previous shyness has faded completely as it leans into your hand. [Pet #1 after Splash]

Koi leans their head into your lap, snoring softly as you stroke their fur. [Pet #2+ after Splash]

You taunt them, bluntly noting that their attacks are weak. [Taunt]

Koi's scales grow dry and fade in colour. [Low HP]




  • Koi was an OC of mine before Undertale's launch in 2015, albeit with a few differences.
  • Originally, the species lacked hind legs, but the idea was scrapped in favor of webbed feet due to designs for most 'catfish' with absent legs.
  • Koi possesses minor hydrokinesis, meaning they have the ability to move and shape water. However, they are unable to use this ability with more than a gallon of water at a time. In addition, it is very taxing on them, only preforming it in rare cases (or when taunted).


  • Koi and this specific species of catfish are property of User:WinterCatzuli and shouldn't be used without her permission.
  • Undertale is property of Toby Fox, all rights reserved.



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