Alternative name: Lizard Blink
Snakes have nictitating membranes, so nictitation is associated with Evil. Nictitation is creepy. Humans expect nictitating species to be evil: sometimes Human prejudice is correct, sometimes not.
Nictitating membranes are additional transparent eyelids that some animals have (snakes, cats, dogs, birds, even camels). Bonus creepiness points because the membrane usually closes side-to-side rather than up-and-down. As a practical matter, they're handy for protecting the eyes from dust or drying out without obscuring vision (even for a moment).
- Zig-Zagged in Star Trek: in that one episode Spock is blinded by looking at a Gorgon-lite. He is saved by the Ass Pull of Vulcans nictitating which is never mentioned before or after, but it does explain why Enterprise Vulcans are such Jerk Ass-es.
- Family Guy: Stewie is evil he builds a machine to create even eviller Stewie. Eviller Stewie nictitates.
- Lord Voldemort in Harry Potter
- The perp at the beginning of Men In Black has a pair. Though they are later explained as being gills.
- Subverted with Chantho from Doctor Who. Friendly and nice