Based on MLP's episode A Canterlot wedding.
Everyone was at the park, enjoying the fresh breeze of wind and relaxing.
"Guys! Alphys send a letter to me! Do you want to hear it?" Sans said.
"Yes." Everyone said.
"Hi Sans, I am inviting you to my wedding with Undyne. Isadora and Toriel are going to make the food, Natasha is going to help me decorate the dancing room, and you are going to check if everything is going fine. Rosa is going to play the wedding music that is Wagner Bridal Chorus on the piano. Janet is going to supervise the flowers for the marriage. Elise is going to bought the dresses for the bridesmaids.
See you all in Sugarland!!!
Everyone got ready and they went to the wedding that was on the castle.
"Alphys!" Sans said.
"Sans!" Alphys said.
Both hug each other.
"So you are gonna marry?" Sans said.
"Yep! Undyne is inside, she is drinking some tea." Alphys said.
"So, you want help with the dancing room now?" Sans offered.
"No, no, no. All you had to do is see if everything is going right. I want you to help on my Bachelor's party after the wedding. Rosa said she is going to help Alphys on her Bachelorette's party." Undyne said.
"Oh boy, I still remember when I met you and Undyne." Sans said.
"You are very clever!" Undyne said.
"I know, I know." Alphys said.
"I don't know why you are my friends. I am just a lazy doofus who make horrible puns." Sans said.
"Don't be silly, you are not a bad person only because you make bad puns or if you are lazy. No one is perfect!" Undyne said, hugging Sans.
"Look, I am afraid that you hate this for being too girly for you two..." Alphys said.
"Don't be like that, there is not games for girls or boys, everyone can join!" Undyne said.
"Moonlight, moonlight, buttetflies awake, clap your hands a do a little shake!" They said, dancing for a few seconds.
The two passed by a cafe, where there was a couple arguing.
"I'm going to the spa and that's it! You cannot stop me!" The woman shouted.
"Shut up! You are always stealing my money! I want a divorce!" The man shouted.
"This is what a toxic relationship looks." Alphys said.
Undyne appeared.
"Hi, Undyne!" Sans shouted happily.
"Oh, hello." Undyne said.
"Do you remember it? Moonlight, moonlight, butterflies awake! clap your hands and do a little shake!" Sans said, dancing happily.
"What is that supposed to mean?" Undyne said with a deadpan expression on her face.
"You do not remember it?" Sans said.
"All I want to do is drink my tea!" Undyne coldly said.
"That was odd." Sans thought.
"Don't worry, she is in such a bad mood this afternoon because of the marriage." Alphys said.
Toriel was making the wedding cake.
"So, how is going with the food?" Sans said.
"Great." Toriel said.
"Taste one of my cupcakes and tell me how it is." Toriel said, giving a cupcake to Sans.
Sans absorbed the cupcake.
"Wonderful!" Sans said.
Undyne came in.
"Hi, Undyne. You want your cake in a round shape or square shape, or heart shape?" Toriel said.
"I want two cakes. One in square shape for me, and one in a heart shape for the guests." Undyne said.
"Hey, took some of my cupcakes with you." Isadora said, giving a cupcake to Undyne.
"Thanks, but I am not hungry." Undyne said, refusing the cupcake.
Undyne was checking the dresses for the bridesmaids.
Rosa, the arctic hare, was choosing the dresses for the bridesmaids.
"How about these?" Rosa said, showing three green dresses.
"Look, I guess green doesn't fit them." Undyne said.
"Undyne, it's her dress, not yours." Rosa said.
"Who cares?!" Undyne said, with a threatening look.
"But I liked the green..." Lily, the red squirrel said.
"Look, I want anything except green dresses! And no more talk!" Undyne shouted, staring on a menacing way at the bridesmaids.
Sans only stared at Undyne.
"Why did she snapped at her bridesmaids just because the dresses are green? That was truly very childish!" Sans thought.
Undyne was with Natasha.
"What do you think about jazz?" Natasha said.
"Perfect, if we were celebrating your party." Undyne said.
"Fine..." Natasha said, hurt with the comment.
"I don't think she is in a bad mood! She must be on her period!!!" Sans thought.
Natasha only stared at Undyne.
Sans was at one of the tables, talking with Rita, the cottontail rabbit.
"Rita, I saw that Undyne is acting in a rude way to everyone here." Sans said.
"Look, maybe she is stressed, because, planning a marriage is hard." Rita said.
Sans only sighed.
"You're so naive sometimes, Rita..." Sans said.
"Okay, I am sorry if my opinion is trash for you!!!" Rita said, walking away.
"Spoiled bitch." Sans thought.
Sans was eating a burrito on the stairs, only waiting for Alphys to came out to show how was her visual.
He heard something.
"You can't do anything, this is my decision! You should stop with this bratty behavior you are having since Sans told me about the bridesmaids dresses!" Alphys shouted, breaking a vase.
"Shut your mouth, mediocre girl. You aren't going to wear this dress, it makes you look like a Raggedy Mandy." Undyne said.
Alphys walked to her bed. Undyne followed her.
"Quit following me!" Alphys said.
Sans slowly looked on the door to see what was going on.
He entered on a room only to see Undyne and Alphys arguing.
"You are NOT going to wear this, are you? Because if you do that, I will break your loved glasses!" Undyne said.
"Shut up, you are acting like a spoiled brat!You can't change my mind, Undyne! I'm going to wear this dress and end of the conversation!" Alphys shouted, holding a blue dress.
"DON'T YOU DARE, ALPHYS!" Undyne shouted, shooting a purple aura from her hands.
The green aura hit Alphys. She looked she was hypnotized.
"Now, go wear your dress. This one you'll wear at home." Undyne said.
"Okay..." Alphys said.
"WHA THE FUCK!?" Sans thought, looking shocked with what he witnessed.
Sans slowly opened the door.
Undyne looked to Sans, confused.
"Huh?" Undyne said.
Sans gave a serious look to Undyne.
"I wanna talk with you, Undyne." Sans said.
"What you want to talk about? The weather?" Undyne said in a sarcastic tone.
"I'm not kidding, Undyne. We really need to have a talk." Sans said.
"I'll be back, Alphys." Undyne said sweetly.
"Alright..." Alphys said, still lying on the bed.
The two were at the cafe.
"So, what do you wanna talk with me?" Undyne said.
"I know that yoy have powers, but I never saw that. What was that green aura coming from your hands?" Sans asked.
"You are asking too many questions." Undyne said, getting off the chair.
"What are you talking about?" Sans said.
"Some things don't need to be revealed!" Undyne said, laughing on a evil way.
Purple flames appeared forming a circle, burning the floor where Sans was, and making it crack and break.
Sans screamed, falling on the dark hole.
The floor was normal like it was cleaned.
Undyne grinned on a sadistic way.
"Hey, where's Sans?" Mettaton said.
"Oh, he said he was going to buy a soda." Undyne said.
"Okay. I just wanna say that Alphys said it's already time for the marriage." Mettaton said.
"Gimme a minute! I have to brush my hair! It's all messy!" Undyne said, running upstairs.
Sans mumbled and woke up.
"Hello?" Sans called.
Sans used his magic to light the place.
"Where I am?" Sans shouted.
"You are on the ruby caves of the Underground, that is now your prison." Undyne's voice said.
"SHUT UP!" Sans yelled.
Undyne's image appeared on some rubies.
"Force me!" Undyne said.
Sans angrily launched his bones attacks at the image of Undyne.
"Over here, idiot!" Undyne said, appearing on a huge ruby stone.
"QUIT MOCKING ME!" Sans yelled, throwing his bone attacks at the wall.
"It's no use. You are trapped here forever!" Undyne said.
Sans throw a bone attack, only to break the huge ruby stone to reveal the real Undyne, with her hair messed and looking battered.
Sans tackled Undyne.
"STOP MAKING FUN OF ME!" Sans yelled, pulling Undyne's hair.
"DON'T HURT ME! IT'S ME, UNDYNE!" Undyne said.
"LIAR!" Sans yelled.
"I am telling you the truth! I am the real Undyne! The fake one trapped me here, trust me!" Undyne said.
"Really? PROVE IT!" Sans yelled.
"Moonlight, moonlight, butterflies awake, clap your hands..." Undyne sang, clapping her hands on Sans' hands.
"And do a little shake...!" Sans completed, surprised.
"I-it's you!" Sans shouted very happy, hugging Undyne.
"Of course it's me! I can't forget my funny and cool friend! But not cooler than me!" Undyne said, punching Sans on his shoulder.
"Why you...!!!" Sans said, jumping on Undyne and wrestling with her.
Both laughed for hours.
"Okay, let's stop. We need to save Alphys! A monster took her from me!!!" Undyne said.
"First we need to get out of here! Alphys' life is in serious danger!" Sans said.
The fake Undyne was at her room, putting the veil for her wedding.
"This day is going to be perfect...since the dinosaur is under my control! Everybody is going to say that I look pretty, the bride is going to be my slave, what they don't know is they are being fooled!" 'Undyne' sang.
"This day was going to be perfect, since Alphys decide to be wife...but instead of being with my friends on the party celebrating, someone is planning Alphys' murder and it's trying to ruin our wedding!" Undyne sang.
"For me, all dresses are only messes, and the cake will taste like crap, only for me smash it on the wall! No, I don't love the bride, and I wouldn't love that fucking dinosaur, but I still want her to be all miiiiineeee!" 'Undyne' sang.
"We must escape and save Alphys' life, before it's too late! I love her so much, that I think she is so cute, oh Alphys dear, my love that I give to you it's trueeeeee!" Undyne sang.
The wedding was happening.
"Finally the moment have arrived, and I'll end with the bride's life!" 'Undyne' sang.
"We'll must save her, before she marry that faker! Alphys is gonna to be..." Undyne sang.
"Mine, all mine!" 'Undyne' said, singing.
The two ran until they found the exit.
Sans and the real Undyne appeared at the room were the wedding was happening.
"STOP THE MARRIAGE!" Sans shouted.
"Get away from Alphys!" The real Undyne shouted.
"Why are you trying to ruin my wedding?" 'Undyne' said.
"Because it's not your wedding, it's MY wedding!" The real Undyne said.
"Why is there two Undynes?!" Doggo said.
"Because she is a faker!" The real Undyne shouted.
"How clever of you, Undyne!" 'Undyne' said.
The body of the fake Undyne revealed to be a grey creature with messy grey hair, humanoid creature and she was wearing a yellow dress.
"I AM SARAH THE SUCCUBUS!" The female creature yelled.
Asgore decide to fight the creature, but he losed.
"King Asgore!" Papyrus said.
"I'm going to be okay. You had to deal with this succubus, now!" Asgore said, before fainting.
"Oh my godness! Outside there it's full of different creatures, and they are all grey!" Papyrus screamed.
Sarah approached a window, looking on it.
"This day was so wonderful. And now everything is ruined and destroyed! Everyone will be my slaves, adult, toddler, or teenager. If they disobey, I will cut their head with a spade. Who said that dreams don't came true?" Sarah sang.
Everyone was outside, ready to fight the strange creatures. But, suddenly, they transformed themselves in forms of the Underground creatures.
"What the hell was that?!" Papyrus shouted.
"Don't question it." Sans said.
"Don't question it." Said the copies of Sans.
"We have to fight against those assholes!" Isadora shouted.
Everyone fought against the demons. Sadly, the monsters losed.
Everyone was on the floor, tied up.
Undyne was tied up, next to Alphys.
"Alphys!" Undyne shouted.
A huge chrysalis was on the ceiling. Isadora was inside of tied, with her eyes covered, and her mouth covered. She was tied up.
A white light came from Undyne's eyes, destroying the ropes, and making her levitate.
"What...?" Papyrus said.
The light exploded brighter, blinding everyone on the room.
After everybody was seeing again, Sarah and the demons were gone.
Undyne launched a rock on the chrysalis, making it break and fall on the ground.
Isadora was okay.
"We have a wedding to prepare." Papyrus said.
Undyne didn't mind the color of the dresses for the bridesmaids. She let them choose the dress they wanted. She even wanted the jazz music for her wedding.
It was night, and Undyne was going to enter on the limo, when she stopped.
"I almost forgot!" Undyne said. She threw the bouquet in the air.
Catti and Dogaressa were going to catch it, when Catty pushed them and catched the bouquet.
"IT'S MINE, MINE! HAHAHAHAhaha..." Catty said, while the bridesmaids looked angry at her.