There are several reasons why the duck may be considered the funniest animal in the world, from its weird, squawky quacks to its squat, stocky body that waggles around when the duck moves around using its feet. The feet itself may be considered humorous, since they look nothing like human feet and seem unwieldy while they are visible on land.
Humans may find animals funny for reasons other than their appearance, though. Behavior tends to be a major point of amusement for people who are observing animal behavior. For example, Internet humor sites often feature images, videos or GIFs of animals doing seemingly silly things, such as making weird faces in a still photograph or "photobombing" a picture in a way that seems calculated. Still photographs may catch animals in the middle of an action in a way that looks particularly undignified, or they may catch the animal with its face in a position that seems to resemble a human expression such as contempt, excitement or fear.