Belongings
The common person would say that Huey was the brains of their family. And they aren't wrong. The eldest triplet was the most academically capable of his brothers – possibly his generation, even.
But academics aren't always relevant to everyday life.
Sometimes the most important things – the most precious knowledge – can only be obtained through savviness and personal discernment.
And that was Dewey's repertoire, not Huey's.
It shouldn't have surprised Scrooge then, really, when Dewey knocked on the door of his office one day (and came in without waiting for a reply). The duckling got straight to his point.
"Does Launchpad's plane actually belong to my mother?"
The mention of Della, even if not by name, was enough to sting Scrooge's ears a little bit.
"What are you talking about, lad?"
"That plane! Was that my mother's, which was passed onto Launchpad when she disappeared?" Dewey pressed on.
"No, that is Launchpad's own property," Scrooge replied, barely concealing a stutter.
"But logically Launchpad – as accident-prone as he is – wouldn't have enough in his salary to pay for his own plane, or the repairs that it always frequently needs!" Dewey explained, in a surprisingly skilled show of deciphering, "So that means it has to belong under your name, really!"
"Okay, lad, yes! That plane is part of my estate!" Scrooge admitted in frustrated humiliation at being caught red-handed.
"And it belonged to my mother, didn't it…?" Dewey asked, trailing off in deliberation.
"And if it did, what makes ye want to brood about that theory?" Scrooge asked suspiciously.
Dewey inwardly cringed and mentally slapped himself. "You seem to have all information about my mother locked up in a metaphorical treasure chest, away from me and my brothers' eyes," he stated in response, cautiously just relaying information that was obvious.
"Lad, have ye ever heard the saying: 'curiosity killed the calf'?" Scrooge questioned.
"Asking information about my mother – that is the right of me and my brothers to know – will not and should not kill me!" Dewey snapped.
"She's gone, lad! And to be straightforward, you and your brothers are lucky enough to have your uncle taking care of you as it is! Honestly, I am surprised and quite relieved to see that my nephew has not started growing grey feathers yet!" Scrooge retorted fiercely.
"I get it – you're trying to guilt trip me into being a good little boy who doesn't question his elders when they screw up!" Dewey fumed, "You don't give a fluff about my mother's belongings – who she was – after that whole Spear of Selene incident – whatever the heck that was!"
"Get out," Scrooge growled. Dewey stubbornly harrumphed at his great-uncle's command.
"Make me."
"Get out of my office, now! Or so help me, I will have Beakley place you under room arrest until I say otherwise!" Scrooge angrily bellowed.
At this threat, Dewey was taken aback – but only slightly. He glared at his great-uncle tearfully as he opened the office door and slammed it on his way out.
From behind the door, Scrooge heard his great-nephew scream, "You can't keep my mother a secret forever, old man!"
But Scrooge didn't reply to this threat. He knew that, eventually, his great-nephew would be proven right.
He could take, hide, and destroy Della's belongings.
But as for her identity, that he could never touch. Even if he wanted to.
Prompt given to me by the lovely acw28.
Prompt was: "Can't wait to see what happens when someone asks Scrooge why he already had an airplane even though he didn't know Launchpad was a pilot."
After a few minutes of thinking, this idea seemed the most obvious to me.
(I hope the show touches on this topic, if this is indeed the case in canon.)