U$53 Interplanetary Postman

Presumably Donald constantly changes dwellings in the stories. At least, his house changes appearance in every story. Known addresses are: 1313 Webfoot Walk (U$05 'The Atlantis Story') and 13 Quack Street (WDCS201 'The Super Dye').
As for Scrooge he is known to live in his Money Bin on top of Killmotor Hill, but before that he seems to have had headquarters in several office buildings. We also learn that he once lived at 1313 Quack Street (U$53 Interplanetary Postman).

U$58 The Giant Robot Robbers

All the Beagle Boys wear visible signs with their prison numbers and this - in some way - helps to identify at least a few of them. Although Barks undoubtedly saw his gang of crooks as one organism without special features some of them can be distinguished; 176-176 is the dumber one, 176-860 takes the lead, 176-761 is well informed and educated, and 176-167 likes cooked prunes!
Now for the big question: How many Boys are there in all? See HERE (bottom part).

U$61 So Far No Safari

The ducks have gone to several auctions in which different sums have been mentioned. It all started in FC0256 Luck of the North where an old trunk was bought for 50 cents, and in U$61 So Far and No Safari Scrooge and Flintheart Glomgold tried to outbid each other for a gold mine. The bids started at one million pounds and two shillings and were raised by one shilling at a time!
In U$17 A Cold Bargain Scrooge managed to buy a ball of Bombastium at the end price of one trillion dollars and six kitchen sinks!

WDCS261 Medaling Around

As we all know Donald has three nephews named Huey, Dewey, and Louie, but Barks happened to draw a fourth nephew 4 times during his long story career. Besides the panel shown above it happened in FC1025 Mastering the Matterhorn and in WDCS0276 Beach Boy (twice!!!). In the USA the extra nephew was soon named Phooey.

DD45 The Dogcatcher

Donald's red car with the licence number 313 was the brainchild of artist Al Taliaferro who drew the newspaper strips for a great many years. Barks used it numerous times in his stories, but in one he made several slips with the number; in U$14 'The Gyro Fence Story' the car switches licence plate number from 313 to being blank to 818.

FC0386 Only a Poor Old Man

The contents of Scrooge's Money Bin is a study in numbers. We are frequently told precisely how much money it contains (Scrooge knows every single coin!), and the figures become more and more elaborate as time goes by. No doubt, that Barks enjoyed inventing the fanciful and incredible figures. HERE they are...

U$06 'The Tralla-La Story'

A rule of thumb in the funny animal comic books is that the characters only have 4 fingers on each hand and 4 toes on each foot, but a few times Barks forgot this unwritten law on the number of extremities.
Examples: In WDCS130 'The Rare Coin Story', WDCS146 'The Omelet Story', and in WDCS159 'The Wispy Willy Story' some of the secondary characters are five-fingered. At least in U$06 'The Tralla-La Story' Barks was consistent; all the inhabitants had 5 fingers!
And in U$52 The Great Wig Mystery one tribe member has 4 toes on his left foot and 5 toes on his right foot...

U$43 For Old Dime's Sake

Personal details such as the ducks' height and weight are very hard to come by as Barks rarely approached the subjects. Still, we have a few references; in WDCS188 'Olympic Tryouts' Donald found himself surrounded by human sized athletes at a sporting event. He reaches up to their hips in height, and in U$43 For Old Dime's Sake Magica de Spell measured Scrooge to be 3 feet tall.
In MOC04 Maharajah Donald Donald is just 2 pounds short of reaching 100 pounds after his feathers had been filled with gold dust. Presumably, he normally weighs in at around 90 pounds (circa 41 kilograms).

FC0282 The Pixilated Parrot

The story about numbers is undoubtedly FC0282 The Pixilated Parrot in which a parrot is seen counting different things during the entire story. But the parrot's 'excuse' for being part of the plot is really that it also remembers the number combination for Scrooge's safe, which, in the end, saves the day!
This was by no means the only time Scrooge needed to remember the combination for his safe. In U$09 The Lemming with the Locket it was scribbled on a piece of paper, and in DBP 'The Impenetrable Money Bin' he had it tattooed on his chest!