The act of putting two Pringles-brand Potato Chips in one's mouth in a way that makes it look like a character has an open Duck's bill. Popularized by TV ads of the chip that showed people doing so.
It can work with other similarly-shaped brands of chips, but Pringles are more likely to stay fully intact, because they're kept in a cardboard tube, instead of a bag. Japan also has a similar brand of stackable potato chips called Chip Star.