3d printed banana for scale but for different scales
"Banana for scale" is a term used on the internet as an excuse to add a banana into a picture you're taking. Since the banana is a recognizable shape of an average size, it's reasonable to determine the scale of an item relative to the banana.
But like, what if the banana wasn't the size of a banana? The entire system would be chaos. Small things would appear large. Large things would appear small! Cats and dogs living together!