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.
The development of Octo Expansion began shortly after the release of Splatoon 2 on July 21, 2017. Series producer Hisashi Nogami wanted to give players an opportunity to explore previously undeveloped aspects of Splatoons world—especially those relating to the Octolings—through a story-driven, single-player adventure. The DLC's levels were designed to be more varied and challenging than those of Splatoon 2s regular story campaign. Octo Expansions visual aesthetics took influence from the popular culture of eras such as the 1980s to elicit a mysterious atmosphere, while its dark, subterranean setting served to set itself apart from the series' colorful world.
Octo Expansion was released on June 13, 2018. It was met with positive reception for its level design, art direction, and story that reviewers said expanded upon the narrative foundations of earlier Splatoon games. Numerous critics deemed it superior to Splatoon 2s regular single-player mode. Many commentators would directly compare gameplay aspects of future Splatoon single-player experiences to Octo Expansion, particularly the base story campaign of Splatoon 3 (2022) and the spin-off title Splatoon Raiders (2026). Much of Octo Expansions cast, including Agent 8, would reappear in the single-player expansion for Splatoon 3, titled Side Order.
Gameplay
Octo Expansion is a downloadable content (DLC) single-player campaign for Splatoon 2. Octo Expansion retains core gameplay elements from its parent title, including the usage of ink as both ammunition and a liquid that players can submerge and swim through. The player controls an Octoling, a humanoid octopus, nicknamed Agent 8. Their mission is to reach the surface by collecting four objects called "thangs" scattered across various testing chambers with differing objectives. There are a total of 80 challenges offered, which includes occasional bosses, but clearing them all is not required to progress the main story. Within the interconnecting hub world, the player can instantaneously travel to numerous stations throughout the Deepsea Metro, which are divided between distinct metro lines. Each station houses a particular challenge and has a mandatory entry fee, which must be paid using the limited CQ Points currency. These entry fees vary across the Metro, ranging from 100 to 3,000 points. If the trial's objective is successfully completed, the player is awarded additional CQ Points. Objectives range from shooting boxes to imitate a desired object, guiding a giant 8-ball to a marked goal, shooting a set number of moving targets, and others. Each level features combat encounters with "sanitized" versions of the Octarian enemies from Splatoon 2s single-player.
Before starting a level, players are offered a predetermined selection of weapons normally found in Splatoon 2s multiplayer, including powerful armaments named special weapons that last for an infinite duration. If the player loses all of their lives, they can reattempt the challenge, provided they have sufficient funds. If they fail more than twice, they are given the option to skip the level entirely. If the player's CQ Points balance depletes below zero by repeatedly failing objectives, they are loaned back a small amount of points to allow further play. Each level is accessed in the hub world through a virtual subway map, displayed through the in-game CQ-80 device.
Upon finishing levels, players are given "mem cakes", miniature collectibles that visually resemble a particular aspect from Splatoons world. Each mem cake is attached to a haiku-structured poem written from the perspective of Agent 8 that centers on the mem cake's subject. The mem cakes can also be exchanged for cosmetic gear items equippable in Splatoon 2s multiplayer. If the player skips a level, its associated mem cake is withheld until said level is cleared legitimately. Collecting every mem cake by clearing each of the 80 available courses unlocks an optional boss fight. Similarly to the mem cakes, players are also gradually given access to in-universe chat logs written by characters Pearl, Marina, and Cuttlefish that divulge background information on elements of Splatoons overarching narrative. Both the mem cake poems and chat logs are viewable through the CQ-80. Once players complete the expansion's story, they are awarded the option to compete in multiplayer matches as an Octoling alongside Inklings.
Synopsis
Setting
The Splatoon series takes place 12,000 years into the far future on a post-apocalyptic Earth following the extinction of humans and virtually all other mammal life, implied to be the result of rampant climate change. After this, the planet is repopulated with evolved, terrestrial marine animals who in the present day reside in the regions of Inkadia and the Splatlands. Such creatures include the Inklings and Octolings, humanoid squids and octopuses respectively, whom players take control of. When a flooding event strikes the planet, the two groups become embroiled in military conflict in competition for land. This conflict becomes known as the Great Turf War. The Inklings, led by general Cap'n Cuttlefish, achieve victory and reclaim all land on the surface, while the Octarians, the overarching group of which Octolings are a part, are forced underground. The single-player campaign of the first Splatoon sees Cuttlefish enlist an Inkling, dubbed Agent 3, to invade Octarian territory to recover the stolen Great Zapfish, the power source of the city of Inkopolis located in Inkadia. Within Inkopolis is the hub world of Splatoon 2, Inkopolis Square. Inkopolis holds regular news broadcasts hosted by a resident idol group; as of Splatoon 2, said group is Pearl and Marina of Off the Hook. The plot of Octo Expansion occurs roughly around the same time as the events of Splatoon 2s base single-player mode.
The Deepsea Metro is a network of subterranean rapid transit facilities owned by the Kamabo Corporation, ran by Commander Tartar. Kamabo's primary activities consist of kidnapping Octarians and subjecting them to rigorous experimental tests. The best-performing test subjects would be killed, with their bodies blended into a fluorescent green paste. This paste, when doused onto other creatures, causes them to lose their memories and free will, ultimately becoming subservient to Kamabo in an act known as "sanitization". Kamabo's ultimate goal is to create an apex species, loyal to the company's ideals, in an attempt to instigate a world of pure harmony and non-conflict.
Plot Under mysterious circumstances, an Octoling becomes confined in an underground subway facility named the Deepsea Metro. They are awoken by former military general Cap'n Cuttlefish, who likewise found himself trapped while on patrol with Agent 3, the protagonist of the first Splatoon. With the Octoling having no recollection of their identity, Cuttlefish decides to assist them in reaching the surface. While exploring the Metro, the duo meet a talking Telephone, who identifies the Octoling as "Applicant 10,008". The title's verbosity prompts Cuttlefish to give them the moniker "Agent 8" instead.
The Telephone relays that to reach "the promised land", Agent 8 must traverse through the subway to collect four objects known as "thangs" scattered across various testing chambers. Agent 8 is given remote assistance via radio by Pearl and Marina of the pop band Off the Hook. Agent 8 clears the challenges and collects all four thangs, which the Telephone combines into a large blender. The Telephone attempts to murder Agent 8 and Cuttlefish by tricking them into entering it. However, heeding a distress signal sent by Marina, Agent 3 breaches the facility, rescues the duo, and incapacitates the Telephone. Agent 8 climbs through the depths of the facility towards the surface, while Cuttlefish stays behind to keep watch over Agent 3, who was knocked unconscious during their attack. Just as Agent 8 is about to reach the exit, they are confronted by Agent 3, who was brainwashed by the Telephone with the use of a turquoise-colored, gelatinous ooze, having also kidnapped Cuttlefish. Agent 8 defeats them in battle, freeing them from their mind control and rescuing Cuttlefish.
After reaching the surface, the trio is retrieved by Pearl and Marina. Upon their rescue, the facility itself begins to rise from the ocean, revealed to be a gargantuan statue of a human. From within the statue, the mangled—but still functional—Telephone formally introduces itself as Commander Tartar, an artificial intelligence constructed by a human scientist before mankind's extinction millennia prior. Initially programmed to encode and pass the knowledge of humanity onto the next sentient race, Tartar became personally disgusted with the cultures of the Inklings and Octolings. Deeming them unworthy of its wisdom, it reveals its new objective: to eradicate all present life and create a new apex species using a genetic ooze made from its past test subjects. As it prepares to discharge a solar-powered cannon from the mouth of the statue to destroy Inkopolis, Marina devises a plan to stop it from charging by having Agent 8 cover the statue in ink. The plan is successful, but the statue fires anyway with its reserve energy. As a last resort, Pearl uses her voice-powered Princess Cannon weapon to counter the laser, destroying both the statue and Tartar. With the threat averted, the group returns to Inkopolis Square.
Development and release Octo Expansions conceptualization began shortly after the release of Splatoon 2 on July 21, 2017. Octolings, which had previously assumed the role of non-player enemies in the series' story campaigns, were considered to be made playable avatars since the original Splatoon and the beginning of Splatoon 2's development. Despite fan interest in the concept of playable Octolings, some players having modded Splatoon to include them, their addition to Splatoon 2 was tentatively rejected as developers felt it would be jarring for Octolings to feature in a non-antagonistic role without explanation. Producer Hisashi Nogami wanted to produce the expansion in part to allow players to explore deeper into the series' world, deciding that a dedicated single-player experience was the best manner of accomplishing this.