"Oh my god, I can't believe you found them!"
"Behold, the power of the internet, my dear Dewford."
"Do you have the hiding place ready, Louie?"
"Sure do. Uncle Donald will never find them here." He tucked the costumes away in the back of their shared closet, way back with all of the clothing they'd grown out of but hadn't gotten around to getting rid of.
"Perfect," Huey said. "Now, remember, this is a secret. No breathing a word about it to anybody, including Webby." He looked at Dewey as he said this.
"What? I can keep a secret!" Dewey said.
"Pff. Says the guy who's had his uncle order his own birthday presents for him for the past three years," Louie said.
"That's different!" Dewey said.
"Either way," Huey cut in. "Nobody says anything about it. Got it?"
"Got it," his brothers chorused.
Dewey ran into their bedroom, slamming the door behind him before throwing his body against it to keep whatever was following him out.
"Webby wants to do group costumes!" he said.
"Tell her we already have our costumes," Louie said.
"She wants to know what they are so she can match!" Dewey said.
"Well, can she keep a secret?" Louie said.
"Probably?" Dewey said.
"I don't know…" Huey said.
"She's not gonna give it up!" Dewey said.
"I still don't think we should tell her," Huey said.
"Why don't you tell her that they're traditional?" Louie suggested. "You know, the standard types of spooky things you see each year."
Dewey snickered. "How is a ghost with a 'pumpkin friend' on his head traditional?" he said.
"I was five!" Louie said, throwing his pillow at his brother.
"That's not a bad idea," Huey said. "It's not wrong, but it's still not giving it away."
"Traditional spooky Halloween monsters. Got it," Dewey said. He cautiously opened the door and ventured back out into McDuck Manor, where he was promptly tackled by one over eager little girl.
"Are you gonna hand out candy this year, Uncle Scrooge?" Huey asked.
"Oh, you should give out king-sized candy bars!" Dewey said.
"In what universe do you think Scrooge McDuck would give away two-dollar candy bars? He might as well just give everybody two bucks," Louie said. "Hey, that's not a bad idea."
"Mrs. Beakley handles Halloween," Uncle Scrooge said.
"Do you think she hands out king-sized candy bars?" Dewey asked his brothers.
"No," said Louie.
"Dang it," Dewey said.
"You do realize you can go to the store and buy one for yourself, right?" Huey said.
"It's just not the same!" Dewey said.
"Want to go shopping for Halloween costumes after school?" Uncle Donald asked.
Huey almost choked on his breakfast.
"No thanks, Uncle Donald," Louie said smoothly. "We already have our costumes."
"You do?" Uncle Donald's face fell, but he quickly forced a smile. Uncle Donald was really big on Halloween, especially the getting dressed up part. "What are you going to go as?"
"It's a surprised!" Dewey said.
Uncle Donald looked confused. "A surprise?" He made a face. "You're not all going to go as me again, are you?"
"You'll see!" Louie said before either of his brothers could respond. The key to keeping a secret was to not answer any questions about it.
"What about a witch?"
"Meh."
"Ooooh, I could go as a pumpkin!"
"Definitely not."
"How about a ghost?"
"Eh."
"Bat?"
"Not really 'traditional.'"
"The Scream?"
"No."
"Spooky clown?"
"Absolutely not!"
"Frankenstein's monster?"
"Now there's a good idea," Dewey said thoughtfully.
"And it'll fit in with your costumes?" Webby asked.
"Yeah, I think so," Dewey said.
"Awesome!" Webby said, running off towards her room. "And I've got the perfect green face paint…"
Why would Webby already have…? You know what? Never mind.
The night had finally come. Webby had run off to her room about two hours ago to put on her costume. Mrs. Beakley was down at the front gate with her supply of goodies to hand out (not king-sized, but still quality candy). And Uncle Donald was downstairs, dressed up as a vampire for the third year running, waiting to take them out as soon as they were ready.
Huey, Dewey, and Louie, had spread out their own costumes on Louie's bed. A devil for Huey, a witch for Dewey, and a ghost-with-a-pumpkin-friend-on-his-head for Louie.
The first time they'd dressed up in these costumes, they hadn't been allowed to trick-or-treat, since Uncle Donald was still very nervous and paranoid and they had been pretty little. A girl dressed up as a witch (with a wart and everything!) had convinced them that Uncle Donald was holding out on them with the good treats (which, she'd claimed, was the real reason he wouldn't let them trick-or-treat, which had made perfect sense to their five-year-old brains), so she helped them pull pranks on him to get them. The next year was the first one they went trick-or treating (wearing the same costumes, since Uncle Donald had been between jobs again).
These weren't the originals, of course, since they'd grown since then, but they were amazingly similar. Huey and Dewey still weren't sure how Louie had been able to get a giant pumpkin hat to go with his own costume.
"Hey! Are you guys ready yet!" Webby called from outside the door.
"Yeah, just a second!" Dewey said, and they quickly put on their costumes before opening the door.
"Wow, you guys look great!" Webby said as Huey held a finger to his lips to signal to her not to give their costumes away.
"Whoa, that makeup is incredible!" Dewey said, looking Webby's green-tinged face. "How'd you get those bolts to stick?"
"Stage glue," Webby said. "And look," she pulled up her bangs to reveal a stitched-up scar, "I even added a temporary tattoo!"
"Kids! Are you ready?" Uncle Donald called.
"Yeah, we're coming!" Huey said. He turned to his siblings. "Ready?"
"Yeah!"
Uncle Donald's face lit up when he saw the kids coming down the stairs.
"Those costumes looked familiar," he said, suppressing a smile. He raised an eyebrow. "There aren't going to be any pranks this year, are there?"
"No, Uncle Donald," the boys chorused, barely able to hide their own grins.
"Nice Frankenstein's monster, Webby," Uncle Donald said. "I like all the green."
"Thanks," Webby said, a huge smile of her own appearing on her face.
"Are you kids ready to go trick-or-treating?" Uncle Donald asked.
"Yeah!" the kids chorused.
"Then let's go!"
Author's Note: The costumes, of course, are based on the short "Trick-or-Treat." I'm almost certain the cartoon doesn't specify which nephew is in which costume, so I guessed based on color (the devil costume is red, and witch costume has a blue shirt, etc.).