Eraserhead 

The "baby" in David Lynch's Eraserhead has no confirmed backstory; its grotesque, inhuman form symbolizes Henry's fear of fatherhood and responsibility, with theories suggesting it's an embalmed calf/lamb fetus or a realistic puppet, but Lynch kept its creation a secret to preserve its mysterious, horrifying power, akin to a magician's trick. Its origins, construction (possibly involving real animal parts or sculpted materials), and its transformation into a planet remain intentionally ambiguous, serving as the film's central unsettling metaphor