Rat

Rats are minor enemies. They relatively easy to defeat, and are found in many Zelda dungeons. They seem to have an affinity for Rupees, and are also possibly related to Real Bombchus.

Characteristics
Rats, as in real life, are shadow-dwelling creatures, preferring dank, dungeonous sewers, wall holes, and even dark rooms in comparison to light-filled areas. First appearing in A Link to the Past, these weak rodents have changed much over the course of the series, though only in behavior; in respect to their appearance, little has differed since their first iteration. Speaking of physicality, the only rats that do not cater to the A Link to the Past look are two variations seen in Twilight Princess, both of which have more feral appearances, however, the Shadow Vermin looks a bit more squid-like, a facet of their appearance that is most likely based in their exposure to Twilight. Rats, since the beginning, have been devious creatures, known to steal and drop Rupees while running about or upon defeat, carry Keys necessary to progress, and toss bombs at unsuspecting victims, the latter of which occurs common in The Wind Waker, where they are known as Bombchu (not to be confused with Real Bombchu in Majora's Mask, although they may be related). Providing the rats with nutrition, such as All-Purpose Bait, will turn the Rats in The Wind Waker into benign creatures; they will talk and politely share some of their wares with Link, whether it be a necessary key or some common pickup item like arrows or bombs. Otherwise, they will run into Link, spilling his wallet all and snatching any dropped Rupees However, this type of wholesome nutrition is not the case with the Rats from Twilight Princess, as they are usually found in cellars and in Arbiter's Grounds feeding off of skulls, a trait not familiar to the rats seen in previous titles.

Ghost-like Rats
The Arbiter's Grounds also acts as the home to yet another rat variant in Twilight Princess: zombie-like rodents known as Ghoul Rats. These ghostly rats cling onto Link and stunt his mobility, and prevent him from jumping off of the edges of a platform. When they cling onto Link as a wolf, Midna will squirm around wildly. The ghoul rats can only be seen and destroyed when using Link's wolf senses. A spin attack can be used to remove them off of Link. Likewise in Spirit Tracks, an extra-terrestrial rat form exists as well, but only at the game's finale, during the fight with Malladus. In Malladus' first phase, Chancellor Cole attacks Phantom Zelda with ghostly rats that tend to home in on her or circle around her. If one of these rats hits Zelda, Cole will take control of her, forcing Zelda to attack Link.

Rats of Freshly-Picked Tingle's Rosy Rupeeland
In the Zelda spin-off, Tingle's Rosy Rupeeland, Tingle will encounter three kinds of rats. At the Hometown Prairie and the Sunshine Seashore, the Green Rat and the Big Green Rat can be found. Once they are defeated, Tingle can receive the Bone. The Big Green Rat is aggressive, while the Green Rat is not. The Black Rat can be found in the Cape Treasure and the Pirate Hideaway. This is an aggressive animal and it won't yield an item once defeated.

Trivia

 * Monsters called Bazu appear in Thieves' Town of A Link to the Past and act very similar to the Rats of the Light World, but are stronger.
 * Also in A Link to the Past a monster called Pirogūsu appears in the Swamp Palace. As well has having similar movement, the latter half of its name, Gūsu suggests a relation with the Gūzu, which is the name given to the Rats in Japan.
 * Syrup and Crazy Tracy from Link's Awakening are the only two characters with rodents in their house. Syrup's Shop and Crazy Tracy's are both located in Koholint Prairie.