Mettaton

Mettaton (/ˈmɛ.də.ˌtʌn/) is a robot with a SOUL and was built by Alphys. Initially poised as an entertainment robot turned human killing robot, Mettaton is later revealed to have only acted as such. Mettaton is the sole television star of the Underground.

Initial Form
Mettaton originally appears as a gray, largely rectangular box with a grid of lights at the top which can change color depending on his various actions. He has four dials along the bottom of his body, and from the bottom, he has a single leg which ends in a wheel. He has two segmented robotic arms which end in white gloves.

Mettaton EX
After having the switch on his back flipped in a Neutral or True Pacifist Route, Mettaton transforms into Mettaton EX; a new body he specially requested Alphys make for him. In this humanoid form, he has black hair with a long fringe that seems to cover his right eye, pale "skin," and visible metal segments below and above his left eye.

He has a pink chest piece with what seems to be a pressure gauge on one side and a set of lights or maybe a speaker on the other, a narrow metallic waist with a box contraption, and black shoulder guards above his segmented arms, which end in gloves. His long black-clad legs end in pink high-heeled boots.

Mettaton NEO
After being confronted by the protagonist on the Genocide Route, Mettaton transforms into Mettaton NEO, which resembles Mettaton EX, but has a more combat-oriented design.

His right forearm is replaced by what appears to be a cannon, his shoulders are clad in pauldrons, which are shaped like legs, and are longer than his arms, and he has wings on his back. The soul on his waist points upwards in a more monster-like manner, and he has a heart shape engraved on his chest plate like Undyne the Undying. His hair on the right side is spiked out, revealing an entirely black segment of his face, with a sparkle or crosshair in place of his right eye.

Personality
Mettaton is a confident, charismatic, and charming TV host that loves drama, action, and violence. He lives for his ratings and adores performing. He supposedly strikes a pose when he does something wrong and makes time on his various shows to beat up "heel-turning villains." He shows a rather shallow appreciation for existence at times. However, despite his seemingly narcissistic personality, he deeply cares about the seemingly positive impact his show has had on the inhabitants of the Underground.

Neutral Route
When meeting Alphys in the Lab, the protagonist is warned about a machine that she had created, Mettaton. Alphys describes it as a robot that was made to be a TV star but eventually had anti-human combat features added (presumably as a way of getting attention from Asgore).

Immediately after this warning, Mettaton bursts through the wall (noted to be only a few feet wide, indicating that he was lying in wait for the protagonist for some time) and forces the protagonist into a deadly quiz show.

Quiz Show
Mettaton asks a series of multiple-choice questions that must be answered correctly within several seconds (the number says 30, but goes down approximately two numbers per second, giving only 15 seconds to answer). If incorrectly answered or not answered within the time limit, Mettaton fires an unavoidable electric shock that does very high damage and halves the protagonist's health. Alphys on the top right will give answers via hand motion; realizing this, Mettaton chooses to humiliate her by quizzing the protagonist on the identity of her unrequited love interest. Regardless of the protagonist's choice, Mettaton ultimately departs, concluding that the quiz show has lost all dramatic tension.

Cooking with a Killer Robot
As the protagonist journeys through Hotland, Mettaton entraps them in deadly pastiches of various media genres. First is a cooking show where Mettaton is preparing a dish (a cake, to be exact) with a human soul as the main ingredient, and attempts to kill the protagonist with a chainsaw to attain it. Alphys calls up and suggests that some viewers may be vegan in an attempt to stop Mettaton from harvesting the protagonist's soul as an ingredient, so instead Mettaton points towards a substitute on top of a faraway cupboard.

However, the cupboard begins to rise from the ground at a rapid rate, forcing the protagonist to use the jetpack feature installed on their phone by Alphys. They will fly to the top and retrieve the substitute within a time limit set by Mettaton while he drops eggs, flour, and milk, all of which slow the protagonist's ascent. Either way, he comments that he was foiled yet again by Alphys. Upon interacting with the substitute after this encounter, it shows the can was stuck to the table, so the protagonist would not have been able to get the substitute given the chance.
 * If the protagonist reaches the substitute within the time limit, Mettaton states he had already baked the cake ahead of time before leaving.
 * If they fail, Mettaton suddenly claims the show is on commercial break and refuses to kill them as there are no viewers.

MTT News
Secondly comes a breaking news segment, in which Mettaton asks the protagonist to report on one of the several items within a room, which all turn out to be bombs hidden by Mettaton. Mettaton then scatters the bombs around the area, and the protagonist is forced to find and defuse all of them with one of Alphys's phone installments before a larger bomb in the center of the room goes off. Regardless of whether the bombs were defused or not, Alphys hacks the big bomb and disables it.
 * If the protagonist defuses all the bombs in time, Mettaton declares that the bomb will now explode in two seconds.
 * If the protagonist has not disabled all the bombs until ten seconds before the big bomb explodes, the time slows substantially.

UNDERTALE the Musical
Thirdly and finally, Mettaton traps the protagonist within a musical, where Mettaton will sing about a forbidden love between him, a monster; and the protagonist, a human. He will mention how sad it is that they must be sent to the dungeon, before opening a trapdoor underneath them into a room with a colored tile puzzle. Mettaton announces that the protagonist must pass the colored tile puzzle within a set time before a line of flame comes at them from the side and burns them to death. Mettaton proceeds to engage the protagonist in battle after the tile puzzle. However, Alphys has one final installment on the phone she had given to the protagonist. This yellow button fires a projectile at Mettaton, which the protagonist can use in succession. Mettaton acts like he is defeated from such projectile and flees. If the protagonist does not activate yellow mode, Mettaton will attack with seemingly unavoidable boxes until the protagonist has barely any health left.
 * If the protagonist manages to complete the puzzle, Mettaton deactivates the flames "knowing" that Alphys would have done so.
 * If the protagonist fails, the flames draw near, only for Alphys to disable them.
 * If the protagonist has stepped on a green tile, Mettaton reminds them that the tile signals a monster, which turns out to be Mettaton himself.
 * If the protagonist has not stepped on a green tile, Mettaton repeatedly says "well" before acknowledging that the protagonist never stepped on a green tile, but still fights them.

End of CORE Encounter
After the protagonist reaches the end of the CORE, they are once more confronted by Mettaton. This time, however, Mettaton reveals that he had re-arranged the CORE and hired monsters so as to attempt to kill the protagonist legitimately. He states that Alphys had set up an extensive plan to self-insert herself into the story because she liked the protagonist so much and wanted to feel important by helping them. All of the previous threats from Mettaton were entirely fake, and everything was acted out, and used by Alphys to ally herself further with the protagonist; Alphys plans to intervene in the fight between Mettaton and the protagonist by "deactivating" Mettaton and thus appearing heroic to them. This time, however, Mettaton has made plans to prevent Alphys's aid, so that he could have an actual battle against the protagonist, and locks the door to prevent Alphys from entering. He explains that he wants to take their SOUL so that he can leave the Underground and become a superstar on the Surface. This way, Asgore cannot destroy the Barrier and re-ignite the war between humans and monsters, which would take a toll on his views.

Mettaton EX
Mettaton attacks the protagonist, but under the advice of Alphys, the protagonist tricks Mettaton into turning around so that they can flip the switch on his back to make him vulnerable. This switch transforms Mettaton into Mettaton EX and begins the true game show. By taking damage, using popular brand items, or using specific ACTs to raise the Ratings of the show to above 10 000 (or 12 000, if he still has legs), Mettaton stops the battle.

To his surprise, this is the highest rated episode he has ever had and begins to take call-ins from viewers. Several callers, the first of which is Napstablook, convince Mettaton that he is highly valued in the Underground, and is the primary (perhaps only) source of entertainment that many of the inhabitants have. He is moved by their passion for the show and decides that he no longer wish to leave the Underground, as well as explaining that the protagonist is strong enough to defeat Asgore. He then deactivates, limbless - whether his limbs fell off during the battle or not - as he runs out of battery power; his body can later be found in the Lab where he is undergoing repairs.

If Mettaton EX is killed, he reverts to his old Mettaton form in the world, though visibly severely damaged. Examining the corpse warrants the description "It's completely trashed."

Mystery Key
If the protagonist purchases the Mystery Key from Bratty and Catty, they can enter the house to the right of Napstablook's. Through a series of diaries, the house is shown to be owned by another ghost known as "Napstablook's cousin" within the game (though Papyrus states that his headcanon name for him was "Hapstablook"). After meeting Alphys, she designed a body for Mettaton to inhabit.

Using the Mystery key during Mettaton EX's fight prompts him to pretend "it isn't there."

True Pacifist Route
In the True Lab, there is a log entry stating that Alphys fears that Mettaton may not talk to her anymore after receiving his new body.

At the end of the game, when all of the Monsters encountered as bosses have united before Flowey intervenes, Mettaton EX shows his leg from the right side of the screen. He tells Alphys and Undyne that they should kiss already since the entire crowd wants it.

After defeating Asriel, if the protagonist returns to Waterfall before exiting New Home, Mettaton will be seen standing outside Napstablook's cousin's house, having recruited Napstablook as his sound mixer and Shyren as his backup singer. During the credits, he is shown on tour, able to use his original box form in conjunction with his new body's legs.

Genocide Route
Mettaton will show up once the protagonist reaches Alphys's Lab and then tell them that he will not battle them, knowing that he is no match for them. He shows up at the CORE and realizes that the protagonist means to not only kill monsters but all of humanity as well. Claiming his main human eradication functions were never fully removed, he transforms to Mettaton NEO. Despite all the buildup, he has no attacks, and the protagonist can destroy him in a single attack. Killing him sets the protagonist's EXP to 50 000, resulting in their LOVE reaching 19.

Contrary to popular belief, missing or inflicting low damage on Mettaton NEO does not fail a Genocide Route. Any attack will deal between 900 000 and 1 000 000 damage, and a MISS will simply cause the game to return to the battle screen.

The only way for Mettaton NEO to say that the protagonist was "holding back" is by failing to depopulate Hotland. Mettaton will point out the protagonist's lack of killing intent, telling them that they are not "absolutely evil" before dying. This event leads to either the Leaderless or Alphys Ending of the Neutral Route.

In Battle

 * See /In Battle.

The Protagonist
Initially, Mettaton actively antagonized the protagonist under the assumption its directive errors into giving it an intensified hate for humans and need to murder them. This was proven to be an act, however, as Mettaton mentions loving humanity, but continued to go against the protagonist on his terms to take their SOUL and prevent a possible war by Asgore. After their battle, however, he was confident the protagonist was strong enough to avoid this themself.

Alphys
Mettaton initially bonded over their common interest in the culture of humanity, and he is grateful of Alphys for making his physical body. Soon after he receives his initial body, he often belittles her and her interests. However, he owed Alphys enough to play along with her plan to act out the role of a genocidal robot before eventually going on his agenda with the protagonist. Despite this, in the ending where he is given the role as king, he mentions how he regrets being cruel to her before she went missing.

Napstablook
Before he got his body, he was Napstablook's cousin, helping them with the snail farm and living next-door to them. They seemed very close, to the point that Mettaton originally declared that he would never leave them behind and often called them Blooky (a trait he kept). Although he had since left them for stardom, he obviously cared for his cousin, looked regretful when Napstablook called into the program to give gratitude for his show ever since he left. Once he had his permanent new body, he immediately recruited his cousin on his tour so they could stay together.

Name
"Mettaton" is similar in pronunciation and spelling to "Metatron," the highest angel in Jewish lore, transliterated into Greek as MTT. It could also be a combination of "metal" and "automaton". It could also be referring to the prefix meta-, which means to change, possibly referencing Mettaton's different forms.

If "Metta" or "Mett" (case insensitive) is typed for the Fallen Child's name, the response becomes "OOOOH!!! ARE YOU PROMOTING MY BRAND?".

"Mettaton" may be a portmanteau of "Meta" and "ton," as Mettaton offers many instances of meta-commentary on the structure of Undertale. Examples include his words turning into bombs, changing the window name during his musical segment, mentioning room numbers before his colored tile maze, discussing Toriel plushies in the epilogue, and offering a newscast to the fourth wall while the protagonist is visible on-screen.

Mettaton's name backward is "Not a ttem", or in other words, Not a temmie. When you fight special enemy Temmie and refuse to give Temmie temmie flakes, the melody of Metal Crusher plays.

Trivia

 * Mettaton's design is similar to other characters not belonging to Undertale.
 * Mettaton's normal form resembles the coin-operated robot Cooker from the Wallace and Gromit short "A Grand Day Out."
 * Mettaton's normal form also has a similar shape to an NES Cartridge.
 * Mettaton NEO resembles Bass's "Treble Boost" form from the Mega Man series.
 * Mettaton is at least partially inspired by Twitter user nerdbotmk2.
 * Mettaton EX's design and attitude are very similar to Maximillion Galactica's, a character from Ace Attorney: Justice For All.
 * The parts on Mettaton EX's chest plate are not a dial and a speaker. During his "heart-to-heart" attack, both of these lose white pixels and appear to act as a locking mechanism that holds his "heart-shaped core."
 * In his box form, Mettaton's overworld sprite has five squares under the main screen, while his battle sprite only has 4.
 * Also in his box form. His clapping animation has disappearing squares under the main screen
 * Along with Flowey, Mettaton is one of the only characters in the game to have a voice clip, exclaiming "Oh, yes!" when he transforms into Mettaton EX, and "Yeah!" when attacked in his Mettaton EX form.
 * Stepping on a green tile during Mettaton's Multi-Colored Tile Puzzle will play the same "Yeah" when Mettaton EX is attacked.
 * Several unused sprites for Mettaton EX's head show his right eye, and what appears to be the machinery on his face.
 * The answer choices to the question What are robots made out of? in his quiz show have several references.
 * "Hopes&Dreams" references the track "Hopes and Dreams," amongst other recurring mentions of this phrase.
 * "Snips&Snails" and "Sugar&Spice" are references to the nursery rhyme "What Are Little Boys Made Of?"
 * Mettaton, at the beginning of the MTT News segment, states that "an interesting situation has arisen in eastern Hotland." The MTT Newsroom is solidly located in central Hotland, and is considerably farther west than other Hotland landmarks, given the length to which Hotland's third floor and the CORE extend east.
 * Mettaton's box form is identical to the console that operates the colored tile maze in Snowdin, and this machine may have been Mettaton himself; during his own colored tile maze, Mettaton remarks that the protagonist has seen the puzzle "ABOUT A HUNDRED ROOMS AGO" and presumes that they remember the rules.
 * During Mettaton's singing performance to the protagonist, the program window is renamed to "UNDERTALE the Musical."
 * The music and the scenario from the musical are a reference for Maria and Draco Opera from Final Fantasy VI.
 * Mettaton EX recognizes answers for "sexy," "foxy," and "tantalizing" in his essay question, but since the X and Z keys cannot be inputted, they are not possible inputs in-game.
 * Mettaton EX originally saved images of all the essays to the computer's hard drive. This feature was removed for being too buggy.
 * According to the Undertale Kickstarter, there were originally plans for the protagonist to have a robot husband, which is presumed to be Mettaton. This feature ended up being cut out of the final version of the game for unknown reasons.
 * Additional evidence that points to this event is an unused variation of the Start Menu that can be found in the game's files and how Mettaton and Napstablook are suddenly included in the full menu.
 * In Undertale v1.001, Mettaton's stats for his box form has been changed from "10 ATK 999 DEF" to "ATK 30 DEF 255".
 * Mettaton and Napstablook are the only enemies in the game that use the Gray Attack.
 * Mettaton is a literal "ghost in the machine." This philosophical phrase is a critique of the perception that mind and body are separate entities when they are actually not comparable; a physical entity cannot be compared to an abstract one.
 * The Mettaton EX fight, according to Toby, was the hardest one for him to design. There were lots of attack ideas for the Mettaton EX fight that were never used, such as more tiny Mettaton robots, and disco dancing robots that threw stars.