Bisuke

is a ninken and a summoning of Kakashi Hatake.

Appearance
He bears an uncanny resemblance to Gaara with a kanji imprinted on his head and dark rings around his eyes. However, where Gaara has the kanji for, Biscuit has the kanji for.

Land of Waves arc
Kakashi called on Biscuit and the nin-dog pack to track and capture Zabuza Momochi. They managed to bite onto the missing-nin and pin him in place. This allowed Kakashi to use Lightning Cutter without fear of a counter attack.

Sasuke Retrieval arc
A short time later, Biscuit and his fellow nin-dogs would be called upon by Kakashi to track down Naruto Uzumaki and his team who had gone off in pursuit of Sasuke Uchiha.

Rescue Gaara arc
Several years later, Bull and the nin-dog pack were called upon to track down the Akatsuki member Sasori using a small piece of his clothing.

Three-Tailed Beast arc
Later in the anime, he is summoned by himself (since Pakkun was busy) to find Naruto, who had gone after Yūkimaru.

Hunt for Itachi arc
During the hunt for Itachi Uchiha, Biscuit was partnered with Sakura Haruno.

Trivia

 * doesn't directly mean "biscuit," which is in Japanese. It could be seen as an abbreviation though.
 * He is known as "Biscuit" in the VIZ-dubbed manga.

Quotes

 * (To Kakashi) "It is very rare for you to summon me."