Exposed Animal Bellybutton

Sometimes when you draw animals on any level of anthropomorphism from Nearly Normal Animal to Petting Zoo People, but especially Civilized Animals, Funny Animals, Petting Zoo People, you just give them a humanlike bellybutton, whether "innie" or "outie," that can be seen through their fur, feathers, or scales.

While some cartoon animals have humanlike bellybuttons, Real Life animals don't have navels like this. Placental mammals beside humans are born with a navel that looks very much like a scar.

Other animals, like monotreme mammals, all birds, most reptiles, amphibians, and fish, most insects, some molluscs, and some arachnids don't have navels, as they are oviparous (were born from eggs). Some squamates (the reptile group that includes lizards, snakes, and amphisbaenians) like rattlesnakes, sea snakes, slowworms, and garter snakes, are either viviparous or ovoviviparous (give birth to live young), as are most sharks, live-bearing bony fishes, some species of scorpion, cockroaches, and velvet worms. They don't have navels as navels are exclusive to placental mammals.

A subtrope of Funny Animal Anatomy and Anatomy Anomaly. See also Nonhumans Lack Attributes.

Comics

 * Subverted in Garfield. The eponymous cat notices a black spot on his belly in the mirror and remarks "I didn't know I had a belly button". Said spot turns out to be a bug, which promptly flies away.
 * Though played straight with some animal characters who appeared in some strips of this comic, especially bigger ones.
 * Pig from Pearls Before Swine.
 * The title character of Pogo.
 * Nearly all the characters in Krazy Kat.
 * When drawn by Steven Butler, Princess Sally of Sonic the Hedgehog tends to have one.

Film

 * Rango the chameleon has a bellybutton.
 * Jiminy Cricket is shown to have a bellybutton in Pinocchio.

Literature

 * In Richard Scarry's Best Little Word Book Ever, the last page gives Huckle Cat this.

New Media

 * Most anthropomorphic art tends to be drawn with this.

Video Games

 * Crash Bandicoot has a bellybutton.
 * This trope is mentioned and subverted in Chrono Trigger. You can try to run from the prison by faking sickness. If Frog is the one faking sickness, he says his bellybutton hurts. After beating guards, he calls them fools for not knowing that frogs don't have bellybuttons.
 * Krystal has one, visible in Star Fox Adventures.
 * The Donkey Kong series seems inconsistent as to whether or not Kongs have them. In some games, they don't have them even when some reptilian characters do.
 * Rouge the Bat from the Sonic the Hedgehog series, although only when she's wearing alternate costumes.

Web Comics

 * In Freefall, not only does Florence (an anthropomorphized red wolf) have a visible belly button, there's even an indentation showing where it's located even when she's dressed in her normal jumpsuit.

Western Animation

 * The Ren and Stimpy Show gives the titular duo these in certain shots.
 * Newton from Neds Newt. He even lampshaded it once: "If newts are born from eggs, why do I have a belly-button?" (beat) "Is a poorly-drawn 'x' an inny or an outy?"
 * Most of the animals in Eek the Cat, including the title character.
 * Oggy and The Cockroaches.
 * Itchy and Scratchy from The Simpsons have bellybuttons.
 * Rodney J. Squirrel from Squirrel Boy has a bellybutton.
 * Almost Naked Animals.
 * Patrick Star from Spongebob SquarePants has a bellybutton.
 * The Fat Bluebird from Homestar Runner.
 * Zee on Noggin
 * The title character of the Robbie the Reindeer specials.