Mettaton
Mettaton is a character in Undertale.
Though he does not make an actual appearance until halfway through the game, Mettaton plays a significant role in the society and culture of the Underground, and the player can find various hints throughout the game that demonstrate this.
Throughout the different regions of the Underground, the player can find some monsters using products labeled as MTT Brand, which Mettaton owns and distributes. And in Hotland one of the areas the player has to traverse is the MTT Resort, a former inn that Mettaton bought and converted into a resort hotel. Whether the player takes the Genocide route or the Pacifist route affects how much more they will learn about Mettaton.
In the Genocide route, the player will meet Mettaton but they won't learn too much about him. Arriving in Hotland, the player will have to pass through the Laboratory to progress. Inside they will meet Mettaton, who will promptly call the player an "ugly little creature" and feign being impressed with their actions thus far. Mettaton will then go on to tell you that Alphys has been busy evacuating the Monsters of the Underground once she realized how much of a threat you are, claiming that she is "the only smart one" for not choosing to fight. When the player steps forward, Mettaton will quickly deduce that you're looking to fight but will leave saying that the world needs stars more than corpses. At the MTT Resort, the cashier for the MTT Brand Burger Emporium will still be there despite the evacuation, and the player can ask him about what Mettaton thinks of it. The cashier will state that part of the reason why he's still working is because of how Mettaton has treated him before; Mettaton would tell him if he should come into work or not, but he often wouldn't tell him until halfway through the shift and then the cashier would be forced to listen to a CD album of songs about how terrible he is at the job. The player will then confront Mettaton again as they are making their way to the elevator in the Core that leads to the Castle. Blocking the way, Mettaton will state that he realized that you pose threat not just to Monsters, but to the entire world. This drove Mettaton to face you again since he needs an audience in order to be a star, and that there are some people he wishes to protect. When the player takes a step forward, Mettaton will warn you that before he became an entertainer, he was built to be an anti human combat robot and hasn't had all of his original functions fully removed. Taking another step anyway, the player will be confronted with Mettaton's combat form, Mettaton NEO, but he will be instantly defeated with one hit with their final words being "Guess you don't wanna join my fan club...?" The player won't see or hear anything more of Mettaton for the rest of the Genocide route.
In the Pacifist route, some of the first major hints regarding Mettaton's influence will be found in the player's interactions with Papyrus. In Papyrus' boss fight just outside Snowdin, after the player starts flirting and suggests going on a date, some of the dialogs will state that Papyrus is putting on different MTT Brand makeup products. And later on during the date, Papyrus will change into his special "dating outfit", which includes basketball shoulder pads that are later on revealed to be MTT Brand fashion basketballs.
The player will meet Mettaton once they arrive in Hotland. Having to pass through the Laboratory to progress, the player will meet Dr. Alphys who will tell them a bit about Mettaton. Alphys will state that she initially built Mettaton to be an entertainment robot, but then gave him anti human combat features for the event that a human falls into the Underground again. Once Alphys started supporting you, however, she sought to remove the combat features only to instead combine them with Mettaton's entertainment features, making him a combat robot that makes a sport out of killing humans. Just as Alphys says that you might not run into Mettaton, a series of metallic stomps will be heard make their way to the Lab and the robot in question will burst through the wall, throwing the player into a life-or-death quiz show. Each time the player gives a wrong answer Mettaton will electrocute you, whereas when the player gives the right answer they'll get their "prize" of more questions. The questions focus mostly on Mettaton himself and some of the other monsters, with an actual math equation and a "guess how many are in the jar" question included to throw-off the player. Alphys will stand off to the side secretly giving the answers to the questions, but when Mettaton asks a question regarding her favorite video game, Alphys will unintentionally blow her cover and Mettaton will decide to ask a personal question about the professor. Seeing that the show has no dramatic tension with Alphys helping, Mettaton decides to wrap up this "pilot episode" and take his leave.
As the player navigates the puzzles of Hotland, they can meet with various monsters who will tell you about their experiences with Mettaton, as well as have more encounters with the robot idol. At the entrance to one of the "ship shooting" puzzles, the player can speak with two adult monsters; one will say that he got to watch the quiz show you were just on, and the other will say that Mettaton is the most popular star in the Underground with a fan club consisting of three dozen members. Soon after, the player will find themselves in a dark room with Alphys calling in to say that she'll hack into the system to turn the lights on. When the lights do come on, however, Mettaton will appear to announce that you are on the premier of the new cooking show "Cooking With a Killer Robot". Mettaton will ask the player to get three ingredients for a cake, only to bring out a chainsaw to collect the final ingredient; a human Soul. When Alphys calls to suggest a substitution to the recipe, Mettaton will state that he just so happens to have some MTT brand human-soul-flavor-substitute on an nearby counter. However, when the player goes to retrieve the ingredient the counter will turn into a tower, and Mettaton will warn that if the player doesn't reach the substitute within the time limit he'll go back to using your Soul for the cake. Mettaton will then use the eggs, milk and flour from earlier to slow you down as you work your way to the top of the tower. Should the player reach the goal in time, Mettaton will admit defeat and leave, saying that he's already prepared a cake beforehand.
The player will next encounter Mettaton when they come to another dark room, only to find themselves on Mettaton's own news program MTT NEWS. The player will then be given several things to choose from to report on, half of which appear to be directly related to Mettaton; an MTT Brand fashion basketball, a video game that Mettaton appears in (which appears to be Undertale), and a movie script for "Mettaton the Movie XXVIII". Once the player picks something to report, however, it'll turn out that everything in the room is a bomb including some of Mettaton's words. Mettaton will then give the player two minutes to diffuse all six bombs, before a single big bomb explodes. Should the player defuse all the bombs in time, Mettaton will come to say that the big bomb won't go off in two minutes but in two seconds instead. When the bomb doesn't go off Alphys will call in to say that she deactivated the bomb, prompting Mettaton to "curse" you and Alphys, but not the eight viewers who remained through the show.
In the following puzzles, the player can find two more resident monsters that you can ask about Mettaton. One will say that they like how Mettaton poses dramatically when things look bad, and the other will say that they like it when Mettaton beats up heel-turning bad guys. These are actually hints the player can keep in mind for the final confrontation with Mettaton, as they pertain to the actions they can take in the boss fight. After the confrontation with Muffet, the player will find a poster advertising Mettaton's latest stage performance which appears to be a parody of "Romeo and Juliet", and it's stated to start soon. Sure enough, when the player enters the next area they will find themselves on the stage for the performance, with Mettaton appearing in a maiden's dress and treating the player as their star-crossed lover. After a musical number about King Asgore's policy regarding humans, the player is dropped into a dungeon where they will be confronted with the Colored Tile Maze puzzle from Snowdin, but with several differences; the tiles will not form a straight path this time, the puzzle space is longer, there is a time limit to how long the player has to solve the puzzle, and there is a wall of flames that will follow the player from behind. Should the player complete the puzzle in time, Alphys will call in to help only for Mettaton to state that you've already completed the challenge, then Mettaton will admit defeat then leave without further incident. Should the player not finish the puzzle in time, Mettaton will announce that the walls of flames will surround you and close-in to burn you. When the flames don't burn the player, however, Alphys will call in saying that she's hacking into the system and tells Mettaton to just give up and leave. To that, Mettaton will remind everyone how the green tiles will call upon a Monster for you to fight, and reveal that he is that Monster. As soon as the battle starts, Alphys will call in to tell you of one more feature she added to your phone; a yellow button that will allow you to shoot bullets that appear to be effective against Mettaton's defenses. Mettaton will say that you've defeated him again but the way he worded his response, and his cutoff "whatever" as he leaves, suggests that all is not as it seems. Should the player go back to the poster advertisement after the battle, the player will find and can speak with a Monster who watched the performance just now, saying that they really liked the dress Mettaton was wearing.
Arriving at MTT Resort, the player can go to an alley outback to meet with Bratty and Catty, where they can learn more about Mettaton in various ways. One way is by talking with Bratty and Catty themselves, where they reveal themselves to be huge fans of Mettaton, to the point that they claim he's their robot husband. The two will also tell you about how while Alphys is the one who "built" Mettaton, Mettaton acts like it was his idea beforehand. On the same note, Bratty and Catty will tell you that Mettaton use to treat Alphys "like an old friend" but they don't act like they're friends anymore. The player can also learn more about Mettaton by purchasing a "Mystery Key" from Bratty and Catty, which unlocks Mettaton's old house. The house can be found back in the Waterfall area, and is the red one next to Napstablook's house. Inside, the player will find six diaries with entries describing Mettaton's life before his robot body was built. The first diary entry states that Mettaton made a promise to the Monster Shyren that the two of them and Napstablook would perform on stage together someday, as means of cheering her up after her sister "fell down." The third diary states that his cousin left Napstablook's Snail Farm to become a training dummy, leaving Mettaton and Napstablook to look after it. Napstablook asked Mettaton if he would ever leave to become corporeal as well, to which Mettaton initially said that he would never leave "Blooky" behind like that as he could never find the kind of body he'd be looking for anyway. The fourth diary states that Mettaton put out an ad for his Human Fanclub, but only had one other person show up to the first meeting, that person being Alphys. Mettaton described her as a dork who was "obsessed with awful cartoons" but found her funny enough to want to meet with her again. The sixth and final diary states that Alphys had surprised Mettaton with sketches of a mechanical body she wanted to make for him, a body Mettaton described as being beyond his "wildest fantasies." The entry ends with "Sorry, Blooky. My dreams can't wait for anyone...", effectively breaking his original promise to Napstablook.
Back at MTT Resort, the player can look around to see various hints about how Mettaton has been since his rise in popularity. The main source of info the player can get regarding Mettaton is, once again, the cashier for the Burger Emporium but you'll first have to actually buy something before you can speak with him. According to the cashier, he came to Hotland because he wanted to work with Mettaton in his performances, but he came to regret it since he instead became a cashier with his talks in the Genocide Route elaborating a little on why. The cashier will also state that all the problems with the resort, such as the fountain in the lobby and the "ingredients" for the fast food, are frequently brought to Mettaton's attention, but whenever someone suggests how they can be changed for the better Mettaton rejects it saying "That's not how they do it on the Surface." Finally, the cashier will state that he now finds it hard to understand why people find Mettaton so attractive despite his body just being a rectangle, even to the point that there are kits meant to help people have a more rectangular body.
After navigating the Core, the player will confront Mettaton on the path leading towards the main elevator. Mettaton will greet you saying that it's time for the showdown to stop the "malfunctioning robot", only to then reveal that it was all an act setup by Alphys. As Alphys watched you traverse the Underground she wanted to become a direct part of your "adventure," so she asked Mettaton to help out by acting like as though he had gone berserk. With that and the reactivation of Hotland's puzzles, Alphys could insert herself as the heroine of your "story." But now Mettaton has grown tired of the "predictable charade," and makes it clear that his only desire is to entertain. So, to give the audience a good plot twist, Mettaton had rearranged the Core's layout without Alphys' knowing and will now keep her from helping you as he will now fight you for real. In the first part of the fight, Mettaton will explain that he's convinced that you won't stand a chance against Asgore, and should Asgore's plan come to fruition, Mettaton would be deprived of the biggest audience of all; humanity. To that end, Mettaton plans on taking your Soul to stop Asgore and then make it big as a star up on the Surface. Alphys will then call in through your cell phone to tell you of a weak point on Mettaton; a switch on his back that'll render him vulnerable should you flip it. Telling Mettaton that there's a mirror behind him, the player will flip the switch causing Mettaton to shake violently and unleash a blinding light. A very prominent "Oh Yes" and a sudden change to the setting, however, indicates that Mettaton has not become fully vulnerable. Appearing as a silhouette amongst stage fog, Mettaton will say that flipping his switch means that his new body will be revealed. As thanks for making the premier happen sooner than scheduled, Mettaton will promise to make your last moments "absolutely beautiful" as he reveals the new Mettaton EX. For this part of the battle, the player has to bring up the ratings of the fight's live broadcast. This can be done by posing dramatically, saying you won't get hit then not take any damage, taking damage after doing a heel turn, eating food from the Burger Emporium, and by playing "fetch" with Mettaton EX. Further more, you'll have to attack Mettaton EX's heart whenever he uses it to attack, slowly damaging his body. Once the player has destroyed Mettaton EX's limbs, he will notice that he currently has the most views he's ever had for any program he's done, enough to have reached the viewer call-in milestone. Opening up the phone lines for his last show, Mettaton's very first caller will be Napstablook who will say that the show had brought excitement into his boring life. Saying that they will miss him, Napstablook will hang up just as Mettaton realizes who it is and tries to keep them on the air to talk. In an attempt to take his mind off of it, Mettaton will allow for another caller only to receive a flood of calls from viewers saying how much they will miss him and his shows. Touched by everyone's messages, Mettaton will decide to stay in the Underground for a little longer as he is the only idol Monsters have. Further more, the fight has convinced Mettaton that you indeed have the strength to make it past Asgore and keep humanity safe, as well as show that his EX form has inefficient energy consumption. Just before his batteries run out, Mettaton will give a heartfelt thanks to his viewers and tell you to "knock'em dead." Alphys will then come in and will initially be shocked by the state Mettaton is in, but will calm down realizing that he just needs to recharge and can easily be repaired. Mettaton will not be seen or mentioned again for the rest of the Neutral route.
In the True Pacifist route, the player will have a few more interactions with Mettaton and even learn a little more about him. Within the True Lab the player can find and read a computer log about the relationship between Mettaton and Alphys during her "Determination" experiments. At that time, Mettaton had made a successful debut as an idol and was so popular he almost never spoke to Alphys again, save to ask her about how his new body is coming along. Fearing that they wouldn't be friends anymore once the new body is finished, and overall feeling very self conscious about working on it, Alphys had been very hesitant about completing that project. Later, when everyone gathers at the Barrier to stop Asgore from fighting you, Mettaton will appear briefly to tell Alphys and Undyne that the two of them should kiss. After the Barrier is destroyed and Chara is fully purged from the player, Frisk can go back through the Underground to interact with some of the Monsters that have been affected by Mettaton's recent actions. In the Core, one of the Monsters that attacked you earlier will say that Mettaton hired them to attack you, but since he hadn't actually paid them for it they're all giving up on it. At the MTT Resort, the cashier will say that Mettaton had told him and all the other employees that everyone is now free to leave the Underground, but that doesn't mean that they can leave work early. The cashier will follow up on that saying that he loves Mettaton, by which he means that he really hates him. At the site of Mettaton's stage performance Frisk will find the Monster that watched the performance, now wearing a dress. Speaking with them will reveal that they were among those who called in during the "Last Episode" boss fight, and Mettaton, recognizing their voice, gave them his performance dress as a "thank you" gift. Mettaton himself can be found outside of his old house back in the Waterfall area where Frisk can talk to him. Mettaton is overjoyed at having his new body repaired and adjusted, just in time for him to finally see the Sun "the greatest spotlight of all." Mettaton will then thank you for the "performances" the two of you did, as they reminded him of how fun it can be to perform with others. In response, Mettaton has been looking for talents to make up his new troupe, with Shyren and Napstablook being the back-up singer and sound mixer respectively. Mettaton will then ask Frisk about what kind of merchandise humans would buy, but after listing off different ideas, Frisk won't have the option to choose any of them and Mettaton will just say that he likes the idea. During the end credits, Mettaton can be seen performing on stage with Shyren, Napstablook and the cashier, fulfilling his promises.