M&M's what?

Hoping to save me from a diabetic coma, my wife took the leftover Halloween candy - mostly mini Reese* cups - to work with her.
But when she called me in to edit copy and do some other work, I found the cache and attacked it greedily. I also found a bunch of trick-or-treat-size packages of those colorful little chocolate candies that melt in your mouth, not in your hand.
As I ripped one open, my eyes fell upon an apostrophe that I never before noticed.
The name on the package is "M&M's."
What?
How can this be? All sentient writers of the English language know that you don't form the plural of anything with an apostrophe.
What the package designer has done, then, is to declared that the contents of the package belong to "M&M." Which begs the question: M&M's what? Little sugar-shelled chocolate candies?

I was stunned and somewhat chagrined that I'd never noticed this before.
So I fired up Google to find out what, if anything, the Ms stand for in M&M.
I seemed to remember the Mars family - the folks who gave us Snickers, Three Musketeers, Milky Way and Mars bars - was involved in it and I was right.
Forrest Mars left his father's successful candy business and struck out on his own, working for a time for Nestle and Tobler in Europe. Some people belive he got the idea for his new candy from sugar-coated chocolate pellets given soldiers in the Spanish Civil War. At any rate, he patented the idea in March, 1941. He did a deal with Bruce Murrie (the other M and a son of Hershey exec William Murrie) that got him access to Hershey's stock of chocolate. World War II was on and chocolate was rationed with Hershey having the enviable position of being the choclatier to the U.S. military.
After the war, Mars bought Murrie out, but kept the M&M name on the product.
Mars died on July 1, 1999, at the age of 95. At the time of his death, his estimated net worth of $4 billion, according to Forbes magazine, made him one of the richest people in the U.S.; his sons, Forrest Mars, Jr. and John Mars are now executives with the company and also said to be worth $4 billion each, along with his daughter, Jacqueline Mars Vogel. Based in Hackettstown, N.J., M&M/Mars employs 30,000 people worldwide with sales of more than $20 billion per year.
But I still can't get over that damned apostrophe.

*And it makes me crazy to hear morons like the counter workers at Dairy Queen prounounce it "Reesy" or "Reesie" cups. Have they never heard of anyone named Reese? Where the last "e" is silent?