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Mad Mew Mew is a ghost inhabiting a robotic Mew Mew Kissy Cutie built by Undyne. She initially posesses and serves as Undyne's training dummy while known as Mad Dummy.

They serve as a minor antagonist in the Hotland arc and the secondary antagonist of the CORE arc, during which she also receives her current body, Mad Mew Mew. After the CORE arc, she becomes a part of Inverted Fate's main cast.



Mad Dummy form

While posessing Undyne's training dummy, they have a red skull with anime-like blonde hair and a green soul headband, red shoulder pads, a 360⁰ metal mouth for a waist and a rocket in the place of legs.

Ghost form

As a ghost, they have the tradition bedsheet ghost look with tears at the bottom. They have a red-orange look with spiky hair to go along.

Mad Mew Mew form

As Mad Mew Mew, she has a metal skirt, keeping her shoulder pads and red eyes, gets a chestplate with a split-soul symbol on it, and FINALLY gets the legs she wanted, along with with a pair of war boots, long pink hair, cat ears, and a cat tail.

She is now armed with a cleaver, and additionally gains the "SOUL Fission" ability, allowing her to "split" combined/amalgamted SOULs temporarily.

This is her first and only form that expresses her true gender identity, with her also switching over to she/her pronouns after inhabiting it.


Mad Dummy gets angry very easily and tends to hold grudges over very little things (for instance, hearing Chara insult them in Hotland and holding it against them and Frisk all the way through the CORE arc). Some of this anger is maintained on purpose in an attempt to fuse with their robot body (and later, Mad Mew Mew body) through strong emotion, but all they just want is Undyne's attention and approval.


One day when Undyne finished making her newest invention, a robotic training dummy, a ghost who snuck in earlier possessed it, claiming it was the perfect body for them. Undyne let them have it for the amount passion they had and the fact that a ghost inhibiting a robot would be a better sparring partner than any AI she could ever code.

Some time later, Mad Dummy overheard Undyne and Alphys watching a Mad Mew Mew anime movie, and they got out of their vessel and snuck downstairs as a ghost. They got captivated by its storytelling and Mew Mew herself. When the credits rolled in the anime and Undyne got up to get the next one, Alphys turned over to the ghost and told them that they could borrow the dvd collection if they wanted. Mad Dummy agreed, thus allowing them to explore Mew Mew more.

Main Story

Hotland Arc

Mad Dummy first appears in Part 29 as a deactivated robot in Undyne's lab. They make their first active appearance in Part 32, where Chara makes a comment about their inability to walk normally. Mad Dummy, being a ghost and thus able to hear Chara, is infuriated and tries to fight Frisk and Papyrus, but is interrupted by Royal Guards 03 and 04.

Later, in Part 33, Mad Dummy appears as the first competitor at the Battle Of The Ages tournament at the dojo, but is knocked out of the ring by Jerry before they are able to attack.


In Part 40, they possess parts of the CORE and continue to antagonize Frisk by possessing machines and the Seasonal Dudes. Eventually, they have a final battle as their original robot body. After failing to kill Frisk in their dummy form, Undyne comes in on the monitor above them and gives them their new form, Mad Mew Mew. The battle continues, and Chara apologies for their insult and encourages Frisk to do the same, convincing Mad Mew Mew not to fight them any more.

New Home & Loose Ends Arc

Mad Mew Mew is seen in Part 52 outside Undyne's old house in Forgespring, complaining that she was locked outside of Undyne's lab and she won't answer any of her phone calls. Papyrus reasons with her saying Undyne endured quite a bit but Mad Mew Mew responds asking if isolation's going to help her, and Papyrus responds again saying he and Frisk don't want to overstep.

Later in Part 54, Mad Mew Mew is seen face-palming during Mettaton's performance, and after it, he mentions Undyne while defending Chara, prompting her to leap from the ceiling and interrupt. She berates Mettaton for constantly humiliating and mocking Undyne and broadcasting her fragile state and her hurting Papyrus to the whole underground. Frisk, Papyrus and Mettaton all argue with her saying Undyne was reckless, took it too far, and the results of her running away were that nobody got hurt. She agrees Undyne took it too far but says she was reckless only because of her desperation to keep her promise. Several other monsters step in to expose several other humiliations Mettaton's done to other monsters, and Mad Mew Mew even says that Mettaton is trying to make the argument about him. Frisk steps in to ask Mad Mew Mew why she's still here if she cares about Undyne so much, prompting her to immediately stop arguing and dash to Undyne's Lab.

True Lab Arc

At the end of Part 56 and in Part 57, Mad Mew Mew fights the Memoryheads possessing a prototype of her body, and Mettaton comes in to destroy it, much to her ungratefulness. The Memoryheads then bombard him with memories and partially possess him. Frisk, Papyrus and Alphys hear her shouting from afar and then encounter her, and she explains the broken Mew Mew robot and complains about Mettaton interfering. Frisk, Papyrus and Alphys attempt to defend him and ask where he is, which she directs them to the next room after they explore.

After the Downward SPIRAL battle, Mad Mew Mew leaps from the ceiling and attempts to fight the Memoryheads, then Alphys tells her they've already been dealt with. Mettaton states what happened and Alphys tries to talk some sense into her, then Mad Mew Mew, Frisk, and Papyrus continue their search for Undyne.

In Part 59, Mad Mew Mew is seen trying to break down the door to Undyne. The Mechamalgamates appear and rush for the lures, crashing and forcing her to jump up. She berates them but notices the open door, and rushes through. She attempts to convince Undyne to live, until Frisk, Mettaton, Alphys and Papyrus come in and the latter two explain they knew Undyne's intentions and explain why they were against them. Mad Mew Mew adds that once you kill someone, there's no turning back and she couldn't follow through with killing Frisk. Mettaton apologizes for broadcasting Undyne's fragile state but she just blames herself for their flawed relationship, but Mad Mew Mew states she loved her training battles with Undyne. Undyne apologizes to the rest of the group and they explain they forgive her, and their plan to destroy the barrier. Mad Mew Mew offers to split Frisk and Chara when Mettaton directs a joke to Chara, though Undyne states she already knows about them. Sans then comes in to apologize and Mad Mew Mew to go away, but Undyne agrees to talk. When Frisk mentions Asriel when referring to Flowey, Mad Mew Mew explains why Flowey is Asriel, and later decides to keep the Mechamalgamates in check.

Victory Arc

To be added



  • She has a much bigger role than in the original game.
    • As Mad Dummy, they went from being a one-off miniboss in Waterfall to a recurring antagonist in Hotland and the CORE.
    • As Mad Mew Mew, she went from being a secret boss and occasional NPC, to a main boss and part of the main cast (implied by Atonement).
  • Mad Mew Mew's inclusion in Inverted Fate as we know it today can largely attributed to the earlier release of Prime Time Turnabout delaying production of the CORE arc to coincide with the release of the Nintendo Switch Edition of UNDERTALE, where her Undertale counterpart first debuted with her new body.
    • According to Dorked, Mad Dummy's character arc would have originally ended with Mad Dummy becoming so angry that they fused with their dummy body.
  • Mad Mew Mew is a transgender woman. Unsubtly, she went from inhabiting a more “rough, edgy" body (potentially serving as a metaphor for an AMAB body) to a more feminine one, also choosing to use she/her pronouns instead of they/them upon obtaining her new body.
  • In comparison to the “human with some cat features" design both her UNDERTALE counterpart and typical depictions of anime catgirls have, Mad Mew Mew has a design more akin to that of an anthropmorphized cat, including a feline-like face and cat nose.
    • According to Dorked, this was the result of Undyne having a bias and wanting to make the body look more “monster-like”[1], resulting in her creating a more cat-like face for the Mew Mew body[2].
  • Mad Mew Mew's voiceblip is sourced from the "nononocat" video, while Mad Dummy's is the same audio but pitched down and slowed.


  1. “Yeah, Undyne wanted to make it more 'monster'.” -Dorked, the Inverted Fate Discord
  2. “IF's Mad Mew Mew has decidedly more cat-like face because Undyne has a bias.” -Dorked, the Inverted Fate Discord"

Main Cast FloweyFriskCharaPAPYRUSAsgore DreemurrNapstablookSansAlphysMad Mew MewMettatonUndyneToriel
Ruins DummyRuins Bullies
Snowdin Dogamy and DogaressaDoggoLesser DogGreater DogSnowdin TrioSnowmanJerryMonster Kid
Waterfall Bassiere von Dohj IIIKnight KnightMadjickRG 01 and RG 02GersonMasaSpout WassarBratty and Catty
Hotland RG 03 and RG 04GlydeSo SorryParsnikAstigmatismMigospelMisyrmMuffetBurgerpants
The CORE Robot 98Robot 100The Season Dudes
Other Characters Fallen humans (The Mage) • W.D. Gaster