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

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

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.