A/N: Alphys lives in a house that is connected to her lab!
Author POV: Papyrus and Mettaton had gotten to know each other more after Alphys' quiz, and learned somethings about each other that they had never known before. Things like Mettaton was originally a ghost and is the cousin of Napstablook and the Papyrus secretly likes puns, just not from Sans, as he's heard them too many times, or if they were bone puns. Papyrus also learned that Mettaton used to be rather shy, but gotten braver after he became corporeal. One day, Papyrus decided to ask Mettaton a very important question.
    Metta POV: Mettaton was as bored as could be as he didn't have any shows any time soon and there wasn't anything on TV. Suddenly, Mettaton's phone went off indicating that he had a text message. "That must be Papyrus! I wonder what he said?", the robot thought. The text read: From Papy💙, "Hey Mettaton, can I ask you a question?" Mettaton got a little worried as Papyrus usually would call him Metta or, when they were looking after Frisk, Ton-Ton, not by his full name. The robot replied,"Sure, you can ask me anything, Papy." Mettaton didn't get an immediate reply, but he knew that Papyrus was typing his reply. After what seemed like forever, Papyrus said,"W-well, we've known each other for about four months now and I was wondering, and I hope I'm not this is too sudden, but would you be my boyfriend?" Mettaton couldn't believe his eyes! Papyrus wanted them to be boyfriend and boyfriend?! Mettaton was so happy! Mettaton almost forgot to answer. But when he did he he said,"Of course, Papy!"
   Papyrus POV: Papyrus had gotten extremely nervous when Mettaton hadn't answered. And what he didn't know is that Sans would've teleported to the robot's house to give him a bad time if it wasn't for Mettaton FINALLY answering. When the nervous skeleton read the text, his face instantly lit up. "He said yes!", the happy and excited skeleton said. "That's great, bro!", Sans said excited for his brother and relieved that he didn't have to give the robot a bad time, as he found that Mettaton was a actually very nice and kind to the two brothers.
(Time skip brought to you by Temmie)
    Mettaton POV: It was the day after the previous events that Mettaton and Papyrus decided to tell there friends. So, Mettaton and Papyrus told Alphys that they were coming over to her lab house with their friends. When everyone got over to Alphys', Toriel ask,"As much as it's great to see you all, why are we meeting at Alphys' home?" Mettaton said,"Ih, you'll find out soon..." Fortunately, Papyrus told everyone after Mettaton had said this, that it was to watch a movie or two. Luckily no one, except Sans, saw the faint orange and pink blushes the two had. (Pink for Metta, orange for Papy.) As the first movie went on, Undyne had fallen asleep. "This will be the perfect way to get Undyne back...", the robot thought, remembering when Undyne had rudely woke him up to tell him that she and Alphys were dating. Though, Sans, Papyrus, Toriel, Frisk, Flowey, Asgore, and Alphys did stare at him when he came back into the living room with metal trash can lids. Sans asked,"What's the trash can lids for?" Mettaton only smirked mischievously. "Mettaton, are you about to do what I think you're about to do with those trash can lids?" Mettaton giggled mischievously and said in a sing-song voice,"Probably!" Then Mettaton walked behind where Undyne was sleeping, raised up the trash can lids and BANG! Undyne woke up with a jolt. She saw that everyone was either laughing, such as Flowey, Frisk (who was try and failing not to laugh), Sans, and Toriel, or smiling and almost laughing. All except Mettaton... Then she realized that there was someone laughing behind her. "Mettaton! What the heck was that for?!",the fish lady said angrily. "Well, you did do that to me, and I simply wanted to return the favor!", the chuckling robot said, smiling. "I hate it when you're right...", Undyne said grumpily. "Anyway, Mettaton and I wanted to share something with guys... and girls.", Papyrus said. "Oh, what is it Papyrus?", Toriel asked. Before either Mettaton or Papyrus could answer, Alphys gasped excitedly and said,"Wait! Are you two...dating?!" Now everyone was staring intently at the two. "Uh...yes? Could you all please stop staring?", Mettaton said, sounding a little nervous. "Oh my gosh!", Alphys said. Soon everyone was excited for the two.
(Time skip brought to you by Muffet)
  Mettaton POV: It had been a week since the two had started dating and there was a new movie playing in the theater. So, the two got tickets and went to go see it. It was surprising to see Sans there too, but he look just as surprised as Papyrus and Mettaton were. He told them that he had bought his tickets online and didn't know that the two would go see the same movie, especially at the same show time. When Papyrus asked Sans why he said "tickets" instead of "ticket", Toriel walked up. Sans then explained, while blushing a little, that he and Toriel had recently started dating and wanted to go see a movie. So Toriel said,"I guess this turned into a surprise double date?" Mettaton said,"I guess it did..." Then the four of them went to the theater and sat down. But what they didn't realize is that this was a horror movie. When the fist scary scene came, Mettaton was hugging Papyrus in fear and he had squeaked before he did. The same was for Sans to Toriel, as the smaller skeleton didn't really enjoy the horror movie. Though he didn't really squeak, he just made a sound of fear. As the movie progressed Mettaton got more scared by the minute, to the point that he was practically whimpering in fear. Papyrus noticed this and wordlessly started petting the frightened robot's head. At first, Mettaton jumped, but after realizing that it was just Papyrus, he started to slowly relax. Soon, Mettaton stopped shaking altogether. Though, he still got scared, Mettaton didn't get as scared as he would have if Papyrus wasn't there. After the movie was over, the four decided to go get something to eat, especially after Sans' and Mettaton's "stomachs" growled. Though it was very cliché, everyone agreed on going to an Italian restaurant. Papyrus obviously ordered spaghetti, but was told by the waiter that the portions were pretty big, so Mettaton asked if the two could split the dish as he was going to order spaghetti anyway. The waiter said that they could, so they did. When everyone got there food and started eating, Papyrus and Mettaton didn't realize that they were eating the same noodle. After awhile, Papyrus noticed this but didn't stop eating the noodle or say anything. But he did text Sans saying,"You wanna see me make Mettaton embarrassed?" Sans saw the text and replied,"I bet you ten dollars that you can't." Papyrus replied,"You're on!" At that point the noodle the two were eating was rather short, yet Mettaton didn't notice. After receiving Papyrus' text, Sans looked up and realized what Papyrus was doing. Papyrus even winked at him! Though he should probably try and stop him, Sans thought it was to funny to pass up. As this was going on, Mettaton was daydreaming. Mainly, it was of what happened in the movie theater, but the daydream was cut short when he felt Papyrus' mouth meet his. At first, he was too shocked to do anything, even after Papyrus pulled away, but soon after his entire face was bright pink. But what the embarrassed robot didn't know not only was Sans handing over ten dollars to Papyrus, but Toriel had take a picture of Papyrus and Mettaton kissing and of Mettaton's bright pink face.
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Mettaton is such a tsundere! And in my headcanon, Mettaton has a very innocent mind. Hope you liked it!~Ash