A simple heads up is all. I purchased Tropical Freeze for the Wii U from Walmart, as a pre-owned game. Of course, they shrink wrap their games so you can't open it just to see what's inside. These days it's getting harder to tell when a recently released game is supposed to include a manual, or slip of paper telling you the manual is in-game, or nothing at all, and it's rather inconsistent.
Super Mario Bros. U included no inserts at all, but the much later Tropical Freeze, is actually supposed to include a full color manual. Luckily for me, I was able to find a thrown out case and manual for this game, but the copy I purchased from Walmart, had no manual inside. This is contradictory to their online policy that all used games do in fact include instruction manuals.
So it's all a bit confusing, but point being, just because Walmart seals up their used copies, doesn't mean that it's actually complete. At least in store.