Ghoul Rats are enemies from The Legend of Zelda: Twilight Princess. These invisible Rats can only be seen when Link is using his senses while in wolf form. Ghoul Rats swarm Link and attach to him, causing him to move much more slowly; they do not, however, directly cause any damage to him. While they are attached to Link in his Hylian form, he will walk as if he is wearing Iron Boots or wading through quicksand. While in his wolf form, Midna will make noise and attempt to brush them off.
The most efficient way to exterminate Ghoul Rats is to wait until a large amount are swarming Link. Executing a Spin Attack while using the wolf form's senses will defeat them instantly.