Mole cricket

The Mole Cricket is a bug in the introduced in. They can be found underground, making a chirping noise. If the player digs where the noise is the loudest, the Mole Cricket is unearthed and will crawl away.

In Animal Crossing
"My my my! Good gracious! This is a frightfully large mole cricket, eh wot? Yes, rather large indeed. Interesting, isn't it? How its monotonous song drags on and on, while the insect itself is nowhere to be seen? That very secret is what sets the mole cricket apart from its relatives. You see, it lives underground, wot wot! It may be because it's become a bit scarce, but I believe that most folk aren't even aware the mole cricket exists. To be nitpicky, it's not actually a true cricket, but rather a distant relative of crickets and grasshoppers. It has rippingly powerful forelegs adapted for digging. In fact, it's these mole-like limbs that give it its name. Its rear legs are shorter than a true cricket's as well. Bleeeeeech! All this talk of bug legs... Simply dreadful! Hooo... But I digress..."

In
When accepting the Mole Cricket, Blathers will impart his knowledge of the bug to the player:

"The mole cricket is a bug, of course, but it resembles a mole! Hence the name. It's clear once you inspect its lower half that it is most definitely a cricket. Blech! Add "imitating moles" to the list of unforgivable things bugs are capable of!

In
Blathers will say this when he reluctantly takes the bug:

"As both mole crickets and moles dig holes, it's said many parts of their bodies ... But the mole is nowhere near as off-putting as this bug... How could they be? Moles don't have antennae."

In
"Mole crickets live underground in tunnels they dig themselves, moving freely through soil. Their forelimbs resemble those of moles and are very suitable for digging. They have large wings that enable them to fly, but they can also swim if the need arises. In the past, people used to think the noise they made underground was actually coming from worms."

In
"Be warned, there is nowhere one might hide from the mole cricket. This plump pest has powerful front claws made for digging holes, and oh how it loves to burrow underground! A cousin to the grasshopper, it also has wings and can easily take to the air. And I swear this on my pinfeathers... Some have even been seen walking on water! Oh mercy, I may need a moment. This is making me feel rather woozy... "

Real-world information
Mole crickets can be found throughout the world, specifically in more temperate climates. They are nocturnal and hibernate during the winter. They are rarely seen, as they live underground in tunnel networks, but are nonetheless regarded as pests. They have large forelimbs that can be used to dig and swim. They are roughly three to five centimeters long and are omnivores, meaning they eat both plants and animals. In some areas of Asia they are eaten, but only when fried. Mole Crickets also appear as a character in another of Nintendo's games: Mother 3.

The Mole Cricket featured in-game is similar in appearance to Gryllotalpa brachyptera, a mole cricket native to Australia, but it could belong to any of the Gryllotalpidae species.