In Norse mythology, Ratatoskr (drilling tooth, sometimes anglicized Ratatosk) is a red squirrel who runs up and down with messages in the world tree Yggdrasill and spreads gossip. In particular, he ferries insults between the eagle Veðrfölnir at the top of Yggdrasill, and the dragon Níðhöggr beneath its roots.
In the Marvel Comics mini-series, Thor: Blood Oath, Thor and the Warriors Three are aided by Ratotosk, who gives them information on how to acquire special apples guarded by the Eagle that resides at the top of Yggdrasill.
In the Christopher Golden novel, Hellboy: The Bones Of Giants, Ratatosk appears as a talking squirrel that provides Hellboy, whose right stone hand is fused with the Hammer of Thor, with critical information several times throughout the novel.
Paul Muldoon's poem "Hopewell Haiku" features the lines, "The razzle-dazzle / of a pair of Ratatosks / on their Yggdrasill."
In the game currently released only in Japan, Shin Bokura No Taiyou: Gyakushuu no Sabata (which would have translated into Boktai 3: Sabata's Counter attack), there is a major enemy named Ratatosk. This continues the trend in Boktai games where many characters, especially villains, get their names from the Norse mythology.
In July 2007, Namco-Bandai revealed the production of Tales of Symphonia: Knight of Ratatosk, a new title for Wii set two years after the events of the original Tales of Symphonia. The story will involve the spirit of the old Kharlan Tree, Ratatosk, and the female lead, Marta, also carries the Ratatosk Core within her.