Mole Men

Beneath the Earth, you can find a strange bunch of people, skilled at digging and with an unusual rodent-like appearance.^[1]

Examples of Mole Men include:

Anime and Manga

Vision of Escaflowne: a mole-man, skilled in digging.
Miss Merry Christmas of One Piece ate the Mogu Mogu Devil Fruit which can make her turn into a mole.

The Fantastic Four's nemesis, The Mole Man, of course! Well, okay, he himself is a disfigured old man (born circa 1904!) who lords over the subterranean Moloids and a select group of giant monsters. There are also various other underground races and societies, including the Lava Men ruled by Grotesk and the Deviants.
Usagi Yojimbo occasionally features a clan of mole-ninjas who are, of course, good at tunneling and popping into or out of escape holes.
The Terries and Fermies in a Scrooge McDuck issue called Land Beneath the Ground!

Atlantis the Lost Empire: Moliere, nicknamed "Mole". Not really a mole, but according to the sequel, he was raised by naked mole rats. Unsurprisingly, he drives a Drill Tank for digging.
The Underminer in The Incredibles

Detailed information about the world of the mole-men is a major part of More Information Than You Require. They live Beneath the Earth, travel around using various Hideous Steeds (and monorails), and worship the Century Toad who lives at the center of the earth. They also were friends with many great Enlightenment thinkers and taught them their beliefs about individual rights and liberty.
Bran Mak Morn's Worms of the Earth

The Ruby radio dramas have The Mole People, led by Moliere. They're extremely fond of terrible mole-themed puns, much to the frustration of one of the main characters.

The official Champions setting includes the Undersea Kingdom of Lemuria, a race of evil megalomaniacs who are all served by their Mole Men slaves. Despite treating the Mole Men like subhuman animals, the Lemurians are dependent on them, because no Lemurian would ever lower themselves to do manual labor, and the Mole Men are the only ones who can repair the technology that keeps their dome-enclosed kingdom alive.

Sam and Max have several mole people. Of note are Shuv-Oohl from "Hit the Road", Harry from the new Telltale seasons, and the immense group of mole people who regulate the planet's temperature in the Animated Series.
The Legend of Zelda Skyward Sword: the Mogma

Girl Genius among the other underground civilizations has Talpini Kingdom under Paris. They seem to be decent folk once peacefully contacted, but unfortunately that's the hard part, since they are somewhat suspicious and xenophobic, and rather infamous for turning intruders into gloves. Authors' comment: "Moooole People! I love Mole People!... <3 --Kaja"
- Also, apparently Gilgamesh hired some.

The Tick (animation) had the Mole People, led by Mole King.
An episode of The Herculoids was called "The Mole Men".
The Simpsons has Hans Moleman, who looks like a mole, and has at least once been portrayed as the King of the Mole People.
Underdog also had an adventure titled "The Mole Men".
In Ned's Newt, there is an entire civilization of "trolls" (pretty much Mole Men under a different name) who often plot to overthrow humanity.
One of the villains from Johnny Test is actually known as the Mole King.
Darkwing Duck's foe Moliarity and his henchmen. Bonus points for being actual moles.