Many animated characters have surprisingly noisy eyes. One can't blink in a cartoon without making all variety of noises. Most likely, these evolved from depictions of blinking in non-moving Sequential Art. Rather than devoting whole panels to a character moving their eyelids up and down, the artist would apply an onomatopoeia or an Unsound Effect to get across the point that the character is blinking. Manga tended to use "piku", while western comics used "blink blink". A subtrope of Wacky Sound Effect. Compare Mickey Mousing, Lull Destruction. Examples of Squeaky Eyes include: