Much like a shark, Pac-Man was a predator who relied on his mouth as his sole source of attack. This would put the tender areas of his face in danger, so it's likely that his large, black, shark-like eyes would also have the shark's trademark filmy secondary eyelid to close over before striking. Though he was a fearsome hunter, Pac-Man was also an omnivore--he fed off live prey as well as vegetation (see cherries).
Therefore he probably had a set of teeth quite similar to a human's: Longer, sharper incisors to the front, with molars to the rear. Because Pac-Man didn't have the razor-sharp claws or other grabbing capabilities we see in most land-based predators, he probably ate most like a snake. This connection strengthens when you notice his trademark gaping maw, which allowed him to swallow prey more quickly and use his stomach to do most of the digesting. This also accounts for the unusual shape of Pac-Man: We're only familiar with the fuller, rounder body because his handlers obviously wanted to use a sedated, well-fed creature during gameplay to help limit aggression and the potential for violence. In reality, the version we are accustomed to would only be seen in a creature that had recently caught a meal. Between feedings, Pac-Man's bulk would be in the form of a deflated cylindrical trail of loose skin, most resembling a used skin-condom.
The Pac-Man's primary food source, it should be noted, is the souls of the recently deceased. When grandpa "passes on," it's possible that instead of "going to a better place" he is actually quickly chased down a dark, twisting crypt corridor by an orb of teeth, before ultimately being torn apart and digested; only his eyeballs left to be callously crapped out onto the cold stone floor.
Supplementary Information: The female of the Pac-Man species is often distinguished by the adorable "bow" on her head. This is another case of dangerous anthropomorphization: The "bow" as we call it, is actually a brightly colored crest. Bright colors and elaborate appendages in nature are often a warning sign to potential predators that the animal is venomous, and to stay away. Nature expert R. DeVoe, formerly of the New Edition Digest, famously authored a report on this phenomenon in an expose published in the early 90s, where he also warned of the female's deviousness by insisting that the creature's elongated teeth, substantial girth and streamlined anterior were all further indicators that one should be wary. This was the "Never Trust a Big Butt and a Smile" system of threat identification as outlined in his greater "That Girl is Poison" treatise.
*Mr. DeVoe was assisted in his research by the esteemed Dr. Biv and Prof. Bel of the New Jack Swing University.
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