I just got to thinking... are Pretzel M&Ms supposed to be like a replacement for those 'Crispy M&Ms" they introduced for like a year in the late 90s (which Orange was the spokesM&M for)?
I wish I could remember the guy's name... there's some guy who wrote a book called "Candy Freak" or something. He went on some local television show and said this about the American candy market... we basically have like 3 major national candy companies, Hershey's, Mars, and Nestle. While they do occasionally come up with a completely new product, for the most part, all new candy bars are alterations of pre-existing ones, swapping out a different kind of chocolate and/or one different filling. And often times, those are just temporary. So basically, we have M&M's, Snickers, Reeses Peanut Butter Cups, Milky Ways, Butterfingers, Crunch Bars Kit Kats, 3 Musketeers, and Twix, and every other candy besides the plain versions are spinoff versions of those, tweaking the size and flavors.
M&M's go through different fillings like no one's business. Some are year round, some disappear, some pop back up for promotional reasons... I'd say they're using Orange as the Pretzel flavor now (why waste a mascot) to answer D'Snowth's question. Now it seems they're working in putting the flavor into the shells as well as the chocolate. I like the coconut M&M's but I think the Hershey's Almond Joy M&M knockoffs are superior due to the fact they actually have coconut in them.
Now if you want a complete freak out list of varieties of flavor a single candy bar can have, look at this
List of Kitkat Flavors, and pay attention to the really bizzarre Japanese ones. They have SAVORY candies!
And to think, all we get is white, dark, standard and maybe that big one if it still exists.