If you end up at Costco when you need to buy ink, you may not be able to remember what cartridge your printer takes.
If you stare long enough at the aisle of options, the number 61 will feel right.
If you get the 61 home, you'll realize you've actually bought a 61XL.
If you put the 61XL in your printer, you'll learn that a 61XL is not the same as a 61.
If this strikes you as ridiculous, you might let out an expression that rivals the tri-color cartridge now sitting useless in the drawer of your writing desk.
If you go back to Costco to buy a regular 61, you'll find out that Costco apparently no longer carries the 61.
If you track down a 61 at Staples, you'll be bugged at how much more you have to pay per cartridge.
And if you know anyone whose printer can take 61XL, you can count yourself ahead of the game for already having a stocking stuffer at this point in the year.
(Clearly this is destined to be picked up as a beloved children's book, at which point I will no longer care how much money I have to spend on ink cartridges.)