People love it when they notice some hinting in Duck comics that show how similar Donald and Scrooge really are (like a picture of Donald diving in jewels is absolutely adorable, etc), and you know what? I think there’s alot more of that in their characters.
Remember the Rosa story “An Eye for a Detail”? The story that focuses on Donald’s incredible ability of noticing even the smallest details on thing that allows him to tell anything apart from other things, including Huey, Dewey and Louie?
Scrooge has that same ability. The main difference between Donald and Scrooge is how they use that skill. Donald is an everyday-man, Scrooge a business-man. They simply need their skills for entirely different things. So while Donald needs his sharp eyes to help him tell apart his nephews, Scrooge needs his sharp eyes to notice fine prints on contracts and flaws in jewels.
There’s other examples too! In nearly every Duck story Scrooge is shown being really careful with his money- he won’t pay any extra, will try to get everything for as cheap as he can to keep his money in the Bin. He’ll even drink rainwater to save money. Scrooge has a good understanding of how economy works, and understands money’s worth. In short, Scrooge knows how to use money as a business-man.
Meanwhile Donald knows how to use money as an everyday-man. Donald is in horrible debts indeed (mostly to Scrooge), and because of it he has to be very careful with the little money he has. At the same time, Donald has to feed and take care of his three nephews, and please Daisy too. So to be able to take care of all these things, Donald has to have a good understanding of how to buy lots of quality stuff (whether it be food or furniture, presents etc) as cheaply as possible.
So while Scrooge knows how to spend his money in a way that he doesn’t have to spend it too much, Donald knows how to spend his money in a way that it’ll be worth it. Again, skill is simply applied differently.
Oh and there’s plenty of other examples, these two are the only ones that I could think of at the top of my head. So there, enjoy the adorable similarities between Donald and Scrooge that can be found between the lines.