Splatoon 2: Octo Expansion is a 2018 downloadable content (DLC) expansion pack for the single-player mode of Splatoon 2 (2017), a third-person shooter video game for the Nintendo Switch. Set in an underground rapid transit system named the Deepsea Metro, the DLC follows an amnesiac Octoling, a humanoid octopus, nicknamed Agent 8. After becoming trapped in the Metro alongside former military general Cap'n Cuttlefish, Agent 8 journeys through a multitude of testing facilities, at the direction of a talking Telephone, with the goal of escaping to the surface.