
Duck or rabbit?
A beak becomes a pair of ears. Nothing in the drawing changes.

A repeated dot pattern contains a hidden three-dimensional shark.
Enlarge the image. Relax your gaze as though looking behind it until neighboring repetitions merge. The intended view uses parallel, or wall-eyed, viewing.
No machine-readable author provided. Fred Hsu assumed (based on copyright claims).
Original file & attribution · CC BY-SA 3.0
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Download imageA repeated dot pattern contains a hidden three-dimensional shark.
Enlarge the image. Relax your gaze as though looking behind it until neighboring repetitions merge. The intended view uses parallel, or wall-eyed, viewing.
When neighboring repetitions are matched between the two eyes, their disparities create apparent depth from a single flat image.