These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
Germans Love David Hasselhoff: The McRib is a popular sandwich with a cult following, but in most countries that serve it, it is only served periodically. In Germany, meanwhile, the McRib is so popular, it's the only country to serve the sandwich year round.
McDonalds also includes (or excludes) certain items based on local tastes and customs. Israeli stores are kosher, Indian stores don't use beef, and stores in China and Hong Kong include wings on the menu. Also, French stores have wine and German stores have beer!
They didn't use drive-through windows until the mid-70s or so. In fact, the first one was installed at a location near a military base, to serve soldiers who couldn't leave their cars while in fatigues.
The Big Mac was introduced in 1968, meaning that it's six years newer than even the Filet-O-Fish. Chicken McNuggets didn't come along until 1983.
The Scrappy: McDonald's is one to various groups: anti-capitalist/anti-globalizaton activists, vegetarians/vegans, environmentalists, health groups (both in terms of the calories of their food and in terms of contaminated food e.g. a nematode worm in a burger) and foodies (especially burger fans), to name a few.
Squick: At some point, customers have found content in their food such as nematode worms, e-coli bacteria, and the back legs of a mouse.
Values Dissonance: When McDonald's first arrived in China, its citizens were baffled by the concept of drive-thru restaurants. In fact, many Chinese simply parked in the drive-thru area and walked into the restaurant to get their food!