Another trick I noticed was the shape of the box they used for the different sizes. The box for the "supersize" fries was tapered at the bottom so the fries wou

Another trick I noticed was the shape of the box they used for the different sizes. The box for the "supersize" fries was tapered at the bottom so the fries wouldn't completely fill the larger box when they scooped the fries in, giving it the appearance of overflowing with fries. As you ate the fries, the remaining fries would slide down and fill the void so it seemed like it was completely full.