Thanks to a run-in with General Traag from Dimension X, the Turtles discover that Krang is experimenting with his "Dimensional Portal" again. Donatello decides to contact the Nutrinos in an effort to discover what Krang is up to. Donatello's "Pan-Dimensional Portal" is knocked "off track" by Krang's machine and instead of Dimension X, the Turtles make contact with an alternate Earth, in 16th century Japan, where animals are the dominant species -- not humans. Suddenly, a samurai rabbit named Usagi Yojimbo is "sucked" through the portal and into the Turtles' Lair. After a short battle, Usagi admits defeat and begs to learn their ninja secrets.