It’s probably best to just watch it first then read about the explanation.
Academic researchers stumbled across it by accident and put forward this explanation:
“The effect seems to depend on processing each face in light of the others. By aligning the faces at the eyes and presenting them quickly, it becomes much easier to compare them, so the differences between the faces are more extreme. If someone has a large jaw, it looks almost ogre-like. If they have an especially large forehead, then it looks particularly bulbous. We’re conducting several experiments right now to figure out exactly what’s causing this effect.”
The way the brain processes vision (called ‘perception’) is incredible and in particular how we perceive faces. Whole chunks of brain are devoted only to perceiving faces and nothing else – incredible.