Mashed potatoes are a non-negotiabale staple at any Thanksgiving table, and they're nearly impossible to screw up . . . right? Turns out, there are a few crucial mistakes you could be making that could make all the difference between smooth, fluffy mashed potatoes and gluey, bland ones. These are eight mistakes to fix if you want to avoid underwhelming mashed potatoes and serve perfect ones that everyone will devour.