Why McDonald's Filet-O-Fish Always Has Crooked Cheese - Tasting Table

"It's because McDonald's trains you to put the top and bottom bun in the top and bottom of the open box, put the ingredients on there, and then instead of placing the top components onto the bottom bun, they just quickly close the box."

"That is why the cheese, a lot of times, is not where it's supposed to be, or the sandwich looks weird because the crew is just closing these boxes as fast as possible, throwing them down the line, and trying to get their orders out."

"When the box snaps shut, the hot fish filet presses down on the half slice of cheese while the buns slide slightly toward each other. Because the cheese is only half a slice and isn't anchored firmly to the bun yet, it can easily shift or fold as the sandwich settles."

The Filet-O-Fish's notoriously misaligned cheese is not a result of careless assembly but rather an inherent consequence of McDonald's sandwich construction method. The sandwich is uniquely built inside its box rather than on a flat surface, with the bottom bun and ingredients placed in the box bottom, then the top bun added before the box is rapidly closed. The quick closing motion causes the hot fish filet to press down on the half slice of American cheese while the buns shift slightly toward each other. Since the cheese is only a half slice and not firmly anchored, it easily shifts or folds as the sandwich settles, creating the characteristic off-center appearance customers frequently observe.

Read at Tasting Table