The source is a Reddit thread discussing a video featuring a young girl demonstrating an impressive ability to quickly spot differences between two nearly identical images. The technique involves crossing the eyes to superimpose the images and create a third, composite image, which then highlights the differences. The thread sparked a lively discussion among commenters about the technique, with many users sharing their own experiences with "crossview" and "parallel view," the two methods for achieving this visual effect. Some commenters, having discovered the technique, shared their excitement and newfound skill, while others expressed skepticism or difficulty replicating the technique. The thread ultimately serves as a demonstration of how readily accessible knowledge and community interaction can quickly turn a seemingly magical feat into a common understanding.