Click the green flag (Turbo Mode highly recommended)
A stage in Scratch is 480 x 360 pixels. The small purple blob you see going back and forth is traveling to every single one of those pixels. At each of those pixels, it is assigning it a color hex between 0 and 16,777,216. While 99.9999999999999655065713% of the creations will look like TV static, there is a 0.0000000000000344934287% chance a recognizable image will appear. Who knows, you may be the one to find it!