Mettaton

Mettaton is a robotic bull 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 so that Alphys could rescue the protagonist, feel important and become closer to them. Mettaton is the sole television star of the Underground.

Initial Form
Mettaton originally appears as a gray, large bull with a grid of lights at the stomach, different to the machine in Sanddin Beach used for Papyrus's Tile Puzzle. The grid of lights can change colors, and Mettaton uses these color changes in place of facial expressions since he lacks eyes and his mouth doesn't move. He has four dials along the bottom of his stomach, and the bottom. He has two segmented robotic front limbs which end in black hooves.

Mettaton EX
After having the switch on his butt getting kicked by Marie in a Neutral or True Pacifist Route, Mettaton transforms into Mettaton EX; a new body he specially requested Alphys make for him. In this cow-like form, he has white "fur" and villainous eyes (making him hate the colour red).

He has a pink chest piece, a narrow metallic waist with a belt contraption, and black shoulder guards above his segmented front limbs, which end in hooves. The chest piece has what appear to be a speaker and some gauge, while the waist has two parts that seem to act as a locking mechanism that holds his "heart-shaped core," as they both lose white pixels during his "heart-to-heart" attack. His long black-clad hind limbs end in pink hooves.

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 forelimb is replaced by what appears to be a cannon, pauldrons clad his shoulders, which are shaped like hind limbs and are longer than his front limbs, and he has wings on his back. The soul on his waist points upwards in a more animal-like manner, and he has a heart shape engraved on his chest plate like Undyne the Undying. He has black segment of his face, with a monster-like design 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 "hoof-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 Tree, the protagonist is warned about a machine that she had created, Mettaton. Alphys describes it as a bull 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 ketchup that halves the protagonist's health. In spite of this, it is impossible to die during this quiz show. Alphys on the top right gives answers via hoof 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.

Cocinar con el Toro Enojado
As the protagonist journeys through Humidland, Mettaton entraps her in deadly pastiches of various media genres. First, he forces the protagonist to become his assistant in a Spanish cooking show where Mettaton is preparing tacos with a human SOUL as the main ingredient, and he attempts to kill the protagonist with a chainsaw to attain it. Alphys calls in as an interruption 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 dragon-flavored substitute on top of a faraway cupboard.

However, the cupboard begins to shoot up from the ground rapidly, forcing the protagonist to use the jetpack feature previously installed on her phone by Alphys. They fly to the top and retrieve the substitute within a time limit set by Mettaton while he lettuce, chicken, and ketchup, 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, like all cooking shows, he had already baked the tacos ahead of time before leaving.
 * If she fails, Mettaton suddenly claims the show is on commercial break and refuses to kill her as there are currently 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 (a parrot, an Ultimate Mecha Strike III video game, a Horrificator movie script, a basketball, a present, and a seemingly normal glass of water), 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 now explodes in two seconds instead of two minutes.
 * If the protagonist has not disabled all the bombs until ten seconds before the big bomb explodes, the time slows substantially.
 * If the protagonist has not disabled all the bombs before time expires, Mettaton states that the protagonist failed to disarm them all within three minutes. However, even factoring in the slower passage of time through the last ten "seconds" of play, the total amount of time given to defuse the bombs still amounts to under three minutes.

During the news segment, a ticker at the bottom of the screen reports the following news.

ANIMALTALE the Musical
Thirdly and finally, Mettaton traps the protagonist within a musical, where Mettaton sings about a forbidden love between him, an animal; and the protagonist, a human. He mentions how sad it is that she must be sent to the dungeon, before opening a trapdoor underneath her 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 ketchup comes at her from the side and squirts her 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 attacks with ketchup until the protagonist has barely any health left.
 * If the protagonist manages to complete the puzzle, Mettaton deactivates the ketchup "knowing" that Alphys would have done so.
 * If the protagonist fails, the ketchup draw near, only for Alphys to disable them.
 * If the protagonist has stepped on a green tile, Mettaton reminds them that the tile signals an animal, 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 her.

End of MOUNTAIN Encounter
After the protagonist reaches the end of the MOUNTAIN, she is once more confronted by Mettaton. This time, however, Mettaton reveals that he had re-arranged the MOUNTAIN and hired animals 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 her. 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 her. 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 her 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 animals, 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 she can kick the switch on his butt 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 limbs), 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 source of entertainment that many of the inhabitants have. He is moved by her passion for the show and decides that he no longer wishes 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 Tree 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 ground beef."

Mystery Key
If the protagonist purchases the Mystery Key from Mrousey and Mousey, she can enter the flower to the right of Napstablook's. The room is primarily purple, with a nest, a star patterned leaf, star-patterned wallpaper, a purple TV, a window, and a star imprinted stem. Through a series of diaries, the house is shown to be owned by another ladybug known as "Napstablook's cousin" within the game (though Papyrus states that his headcanon name for him was "Samuel"). 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 Tree, 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 Animals encountered as bosses have united before Flowey intervenes, Mettaton EX shows his limb 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 Coral Reef before exiting New Home, Mettaton is seen standing outside Napstablook's cousin's flower, having recruited Napstablook as his sound mixer and Shyfish as his backup singer. During the credits, he is shown on tour, able to use his original bull form in conjunction with his new body's limbs.

Genocide Route
Mettaton shows up once the protagonist reaches Alphys's Tree and then tell her that he will not battle her, knowing that he is no match for her. He shows up at the MOUNTAINand realizes that the protagonist means not only to kill animals 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 her LOVE reaching 19.

Contrary to popular belief, missing or inflicting low damage on Mettaton NEO does not fail a Genocide Route. Any attack deals between 900 000 and 999 999 damage, and a MISS simply causes 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 Humidland. Mettaton points out the protagonist's lack of killing intent, telling her that she is not "absolutely a tiger" before dying. This event aborts the Genocide Route and leads to either the Leaderless or Alphys Ending of the Neutral Route.

Mary
Initially, Mettaton actively antagonized the protagonist under the assumption its original purpose as a human eradication robot along with directive errors gave it an intensified hate for humans and a need to murder her. 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 her SOUL and prevent a possible war by Asgore. After her battle, however, he was confident the protagonist was strong enough to avoid this herself.

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 her with the dragon farm and living next-door to her. They seemed very close, to the point that Mettaton originally declared that he would never leave her behind and often called her Samantha. 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 she could stay together.

Trivia

 * If "Metta", "Mett" (case insensitive) or "MTT" is typed for the fallen child's name, the response becomes "OOOOH!!! ARE YOU PROMOTING MY BRAND?".
 * Undyne holds a spear in her right fin, and Mettaton NEO has an arm cannon replacing his right hoof.
 * Along with Flowey, Mettaton is one the characters in the game to have a voice, 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 Multicolor Tile Puzzle plays the same "Yeah" when the protagonist attacks Mettaton EX.
 * Mettaon looks feminine in his EX form, but he looks like a Minotaur in his NEO form, also he lacks white parts.
 * The translation for "Cocinar con el Toro Enojado" means "Cooking with the Angry Bull" in Spanish.
 * Mettaon was voiced by Clancy Brown. Clancy gave the voice for Asgore from ANIMALTALE, Eugene H. Krabs from SpongeBob Squarepants, King Frederic from Tangled: The Seris and Doctor Neo Cortex from the Crash Bandicoot seris.