Huh? You don't recognize me...?
Ohhh ho ho…
That's all for the better~!
Once I fuse with this PERFECT new body, mew~
A brand new, WONDERFUL life is going to begin!
Mad Mew Mew before her battle
Mad Mew Mew is a secret miniboss in Papyrus and Sans's House in the Nintendo Switch version and the monster behind the poker table (after defeating Mettaton) in the Xbox One and Xbox Series X|S versions of Undertale.
Mad Mew Mew appears in one of three dresses when first encountered. She appears in the same dress during the fight she wore when revisiting her in front of Undyne's House in the epilogue of the True Pacifist Route. In battle, Mad Mew Mew has a human-like body with a cat tail. She wears a frilly tutu, a t-shirt, and a pair of ballet shoes. Her head is able to come off when the player attacks her, which she catches in her hand and puts it back where it was.
Just like when she was Mad Dummy, she is constantly angry and a bit rambunctious. She has a tendency to make violent threats and repeat herself three times in a row. Humorously, she also has a new habit of adding "mew~" to the end of certain sentences. It is unclear if this is a conscious decision made to better coincide with her new body or if it is an innocuous side-effect of the possession.
After the fight against Mad Dummy, its ghost possesses a Mew Mew doll and unsuccessfully attempts to fuse with it. According to them, the doll was found in a "sciencey place", which heavily implies that the doll belonged to Alphys, a fan of Mew Mew Kissy Cutie.
Nintendo Switch version
When the protagonist accesses the Dog Shrine by entering through Papyrus's sink, they find it abandoned and destroyed with the Annoying Dog in the middle of the wall replaced by a door. The door has a mysterious seal on it and colors corresponding with the Nintendo Switch's Joy-Con. This seal falls off after defeating Mettaton EX and can be opened by moving both analog sticks apart from each other. Inside is a small room with a Mew Mew doll in the center. Interacting with it and then either attacking or touching the doll multiple times initiates the fight.
In the Xbox version, the Dog Shrine has been overhauled again, meaning that Mad Mew Mew can no longer be fought. Instead, she appears behind the poker table after defeating Mettaton EX, replacing Sans. She gives her own commentary based on whatever the protagonist last interacted with.
True Pacifist Route
On the Nintendo Switch version, after the fight with Mad Mew Mew, the training dummy in front of Undyne's house disappears (regardless of whether the protagonist chose to fight or spare Mad Mew Mew) until the True Pacifist ending is achieved, where Mad Mew Mew appears in front of Undyne's house. During the True Pacifist Ending Credits, Mad Dummy's character credits have been replaced with Mad Mew Mew's.
- If Mad Mew Mew was spared
- You…! You!!!!!!
- Thanks a lot for your help earlier, mew~
- I'm starting to feel GREAT in this new form!!! I want everyone to see it!!
- Who knows, maybe I'll even start my OWN TV show and take the world by storm!
- Watch out, Mettaton!!! I'll STEP on your puny metal behind!! Hahaha!!!
- … … hey, do you think Undyne's going to come back here soon, or...?
- Isn't it NORMAL to think a lady might want to watch her own house burn down!?
- It's sort of like, er, your own personal fireworks show! VERY personal!
- If protagonist attacks Mad Mew Mew
- You thought you could stop ME from using this body!?
- I may be in pieces, but I still gotta be myself!
- Your days are numbered, mew~
- When Undyne asks if anime is real or not during the date with Alphys, the answer that the protagonist gives alters the name of the border that is given at the end of the encounter with Mad Mew Mew.
- If the player has not yet reached that point, the border can be selected, but the name of the border is blank.
- Due to her addition, there is now a fight in all 4 main areas of Undertale that use the Ghost Fight leitmotif (Napstablook in the Ruins, Mad Mew Mew in Snowdin, Mad Dummy in Waterfall, and Muffet in Hotland/CORE.)
- Her face sprite is separate from her head sprite, similar to Temmie.
- Similar to Napstablook in the Ruins, Mad Mew Mew hides in the Dog Shrine to be alone, and if the protagonist shows kindness, ends up making a friend instead.
- Although she is described as a life-sized doll during most of the fight, she is revealed to be an animatronic character once she is defeated violently.
- She is described as limited-edition, implying that she was made on the Surface like other Mew Mew Kissy Cutie items Alphys collects.
- (It'll probably naturally fall off by the time your journey is nearly over.) - Narrator