Polymer plastic money definitely has a lot of advantages. So does having multiple sizes.
Honestly, I don't know why US continues to use cotton-based banknotes and the same size for all of its denominations. I also don't know why we continue to use the imperial weight and measurement system, rather than just hop on the metric system like the rest of the world.
The yellow spot is a watermark area with an image of Benjamin Franklin. The "squid" thing (I think) is the quill used to sign the Declaration of Independence.
Honestly, I don't know why US continues to use cotton-based banknotes and the same size for all of its denominations. I also don't know why we continue to use the imperial weight and measurement system, rather than just hop on the metric system like the rest of the world.