The Deceased D

Q. I saw a sign in a fast-food joint which promised tasty French fry potatoes. Is that right?

A. Hmmm….what happened to the -d in Mickey D? It's wrong; the correct spelling is fried. I'm beginning to see this error in many places, often connected with food for some strange reason. Recent sightings include hot butter popcorn (buttered), cream spinach (creamed), a use car (used), can corn (canned), and distinguish writers (distinguished). Sadly, that last one was on a university web site.
These are all adjectives formed from regular verbs, specifically from the past participle. Usually, they describe persons or things which are receivers of an action or process, and what they have received is basically completed. Something was done to them and they are changed. The -d ending adjective tells what kinds of persons or things they have become as a result of what happened to them. Consider the matter sign, seal, and deliver.