Rebecca was walking with Huey and Louie down the hall to the boys' room. They were looking for Dewey because of what the middle boy was trying to pull. A 'Day of the Only Child'? Really? It was stupid, and asking for trouble, especially with-
"Give it up, Dew-pelganger! Where... is... Dewey?" Webby demands from inside the room.
"There it is!" Rebecca remarks as they rush into the room, where Webby is trying to kill Dewey.
"Webby, stop! That is Dewey!" Huey says as he pulls on Dewey's arms.
"He's just doing a Dewey thing!" Louie adds as he grabs onto Huey.
"Meaning trying to get himself killed!" Rebecca adds as she tries to pull Webby off.
"Oh." Webby says as she releases the boys, who fall back in a pile.
Dewey stands and dusts himself off. "Thank you, good Samaritans. You restored my faith in the kindness of random strangers."
"Not even one hour in, and your stupid 'Only Child Day' has already almost gotten one of us killed." Huey says, annoyed.
"'Only' -what-now?" Webby asks confused.
"It's a beautiful holiday." Dewey says.
"That he made up." Huey corrects.
"Where, for a whole day, we get to be sibling-free," Dewey explains as he picks up Webby and twirls her, "and do all the amazing things," before placing her down, Webby a tad dizzy, "that an only child gets to do! Make our marks on the world!"
"Not have to answer to anyone!" Louie says.
"Be horribly alone?" Huey and Rebecca question.
"For once!" Dewey cheers, to which Huey pushes him away.
"He's been threatening to do it for years," Huey says as he walks over to Webby, Rebecca, and Louie, pulling a WaddlePad out of his hat, "but I never thought he could get into my password-protected sibling calendar."
Dewey then grabs the WaddlePad. "I have my ways." He says as it is revealed he just drew on the screen in black marker, which makes Rebecca facepalm.
"You can't just-" Rebecca starts, but is cut off by Huey.
"Of course, he put it on the day I need them both, the annual Junior Woodchuck Three-Man Cookout." Huey complains.
"Boring." Louie remarks.
"Ugh. Teamwork." Dewey complains.
"But-" Rebecca starts, but is cut off as Louie starts to talk.
"Well, as the now sole heir to Scrooge's fortune, I can finally make friends with Doofus Drake, the richest kid in Duckburg. He only mingles with other obscenely rich heirs, so..." Louie shrugs.
"What a snob." Huey says.
"He's the worst." Dewey remarks.
Louie gasps dramatically before turning to Webby. "You see the judgement that I have to live with? Well, today, your heartless criticism can't deny me my dream of being shamelessly spoiled."
"What are you gonna do, Dewey?" Webby asks the blue sibling.
"Can we just-" Rebecca starts, but is cut off by Dewey, as each time she gets more and more deflated, shrinking back.
"I don't have to explain myself to you! I'm an only child!" Dewey says proudly.
"I don't get why you're doing this. Isn't being a sibling awesome?" Webby asks.
"Thank you!" Huey and Rebecca say.
"Who are you again, sassy stranger?" Dewey asks arrogantly.
"Guys-" Rebecca tries to intervene.
"The brother you rudely take for granted! Right, Louie?"
"Can't we-"
"The random passerby clearly love Only Child Day, right, Louie?" Dewey then stammers, "Or, whoever you are?"
"This isn't-" Rebecca tries to plead as she gets more and more distressed.
"I just want to use a rich kid for his infinity pool!" Louie says as she cries spoiled. "Why can't I have that for myself!"
Huey and Dewey then start to physically fight, rolling around on the floor.
"Stop fighting! Stop it!" Louie pleads.
"And this is why we need Only Child Day." Dewey 'justifies', as Huey slaps him.
"Wha- buh- we-" Rebecca starts to hyperventilate, eyes wide as she, mentally, starts shutting down at the thought of her family breaking up for even a day, and them fighting over something so... stupid.
...
Webby was walking around the manor in a huff after the boys went their own ways. How could the guys just, split up? How could any siblings? As a de facto only child, they were right when Dewey said she didn't understand, but it didn't mean she was wrong. While she was wondering how to get them back together, she hears something coming from a nearby room. "Uh, hello?" She opens the door carefully, only to find Rebecca, who was rocking back and forth in fetal position, in a state of severe distress as she mutters to herself.
"Rebecca? You okay?" Webby asks as she walks up to the oldest quadruplet.
"Of course I am. W-why wouldn't I be? Hahaha." She says with a slightly twitchy eye, looking a tad crazed.
"Uh... You sure?"
"Abso-" Rebecca's expression changes completely, to being almost emotionally broken. "No, I'm not! I just get three baby brothers after ten years of being an only child, and they wanna split up? How could they? We're family!" She starts to break down.
"Hey, hey, don't cry." Webby says, patting Rebecca's shoulder
"I'm not crying. I just have something in my eye." Rebecca sniffs, wiping her tears away.
"Is that something feelings?"
"... Maybe... But I have a right, I don't wanna lose my brothers, not again!" Rebecca says as she fully breaks down.
"Okay this is too far! I am going to stop this madness once and for all! Starting with the one who started this."
"Please don't kill them Webby."
"I won't. Just scare them." Webby assures, leaving Rebecca, who resumes her panic attack.
...
Later, after Webby gets the brothers back together with the help of the DT-87 robot and returns home with the three...
"Rebecca! We're back!" Webby calls, the trio of brothers behind her.
Rebecca perks up and immediately rushes past Webby and to the three. "Guys!" She bear hugs her brothers, before conking each on the head.
"Ow!" The three cry out collectively, rubbing their heads.
"Don't, EVER, do that to me again! Ten years without you, and you just abandon me?"
"Aban- sis we weren't abandoning you!" Dewey says.
"Sure felt like it! Only Child Day? We're family!"
"We just needed a day to ourselves." Dewey adds.
"Yeah, after ten years of being trip-lets... oh..." Louie realizes, inhaling with guilt.
"Which we aren't anymore. We're quadruplets now, with a sister who hasn't had us for ten years... Who doesn't see the need for us to split up you guys see what I mean?!" Huey says, furious at his brothers causing their sister distress by insisting on this even after he dismissed. "Your selfishness hurt our only sister!"
"Sis... we didn't- I... why didn't you speak up?" Dewey tries to argue, but is too ashamed to be accusing.
"You guys were arguing, I couldn't get a word in. That, and I don't do good in confrontations like that." Rebecca says. "I tried to speak but, you each cut me off and I didn't want to interrupt."
"She has a, really, hard time with that kind of stuff." Webby explains. "That, and she loves you guys. You're her family."
"I lost you guys once. I can't lose you again." Rebecca says, almost whimpering.
The boys look ashamed, it finally hitting them how they've been leaving out there sister on so much.
"Okay, so Day of the Only Child is a no-go... Ooh! I got it!" Dewey says.
"What?" Huey asks, skeptical.
"Only Brother Day! Yeah! Where we spend a day alone with our older sister!" Dewey says as he puts an arm around Rebecca.
"Uh, Dewey? There's three of us and one of her?" Huey says.
"Your point?"
"How can it be 'only brother' if all three of us are with her?"
"Well..." Dewey realizes and looks, grabs Rebecca's arm. "I call dibs!"
"Like she'd want to be with the one who caused and started all this." Louie grabs her other arm. "I should spend the day with her!"
"Neither of you should because you are being childish right now and both wanted it. She'd be better off with me, the one who opposed all this nonsense?" Huey says, getting between his two brothers and trying to push them off their sister. At this point, Rebecca is getting annoyed as the three start to argue and bicker, eventually pushing and shoving. Finally...
"PERSONAL SPAAAAAACE!" Rebecca screams, her brothers releasing her startled, the girl's eye twitching. "How about we NOT split the family? At all? Okay?"
The boys nod, frightened.
"Good. Now, I'm going to calm down by watching some anime. Alone. Because you three are a tad insufferable to be around at the moment." She starts to leave. "Oh and if I catch wind of or witness you fighting over family, the perpetrators must fight me, hand-to-hand... to the death." She finishes before returning to her room.