Set in an underground rapid transit system named the Deepsea Metro, the DLC follows an amnesiacOctoling nicknamed Agent 8. After becoming inadvertently trapped in the Metro alongside former 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 ran concurrently with Splatoon 2's series of free updates. Series producer Hisashi Nogami wanted to allow players to explore previously undeveloped aspects of Splatoon's 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 Splatoon 2's regular story campaign. Octo Expansion's visual aesthetics took influence from the popular culture of eras such as the 1980s to elicit a mysterious and nostalgic atmosphere, while its darker, subterranean setting served to set itself apart from the series' otherwise colorful world. Its soundtrack was deliberately arranged to be minimalistic and experimental to further deviate Octo Expansion from previous Splatoon titles.
Octo Expansion was met with positive reviews for its difficulty, unique artistic vision, and story that reviewers said expanded upon the narrative foundations of earlier Splatoon games. Numerous critics deemed it superior to Splatoon 2's regular single-player mode.
Map of the Deepsea Metro as seen in-game, featuring its 80 available levels across numerous metro lines.
Octo Expansion is, like past Splatoon installments, a third-person shooter, and retains core gameplay elements like the usage of ink as both ammunition and a liquid that players can submerge and swim through.[1] The player controls an Octoling, an evolved humanoid octopus, named Agent 8. Their mission is to reach the surface by collecting four objects called "thangs" scattered across various challenges with differing objectives.[2] There are a total of 80 challenges offered,[3][4] which include occasional bosses, but clearing them all is not required to progress the main story.[1] 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; said fees can vary from 100 to 3,000 points depending on the level's difficulty.[5] If the trial is successfully completed, the player is awarded additional CQ Points, but gain none if they fail the objective.[6] These objectives range from defeating enemies within a given time limit, guiding a giant 8-ball to a marked goal, and shooting a set number of moving targets.[7][8][9]
Before starting a level, players are offered a predetermined selection of weapons normally found in Splatoon 2's multiplayer, including powerful armaments, named special weapons, that last for an infinite duration.[10] The weapons are categorized by their mechanical difficulty. Clearing the objective with a more difficult weapon grants the player a greater number of CQ Points than if they were to select an easier alternative.[5] If the player loses all of their lives, they can reattempt the challenge, provided they have sufficient funds. If they fail at least twice, they are given the option to skip the level entirely.[11] If their CQ Points balance depletes below zero, they are loaned back a small amount of points to allow further play, functioning akin to credit.[12] Each level is accessed through a virtual subway map, displayed through the in-game CQ-80 device,[13] accessible only in the hub world.[14]
Upon finishing levels, players are given "mem cakes", miniature collectibles that act as manifestations of Agent 8's lost memories[6] and which visually resemble a particular aspect from Splatoon's world, typically a character.[15] Each mem cake is attached to a haiku-structured poem written from the perspective of Agent 8[16] that centers on the mem cake's subject.[17] The mem cakes can also be exchanged with an in-game vendor named Iso Padre for cosmetic gear items equippable during Splatoon 2's multiplayer.[5] If the player skips a level, its associated mem cake is withheld until said level is completed legitimately.[1] Collecting every mem cake by clearing each of the 80 available courses unlocks an optional boss fight.[17] Similarly to the mem cakes, players are also gradually given access to in-universe chat logs written by characters Pearl, Marina, and Cuttlefish that offer background information on various elements of Splatoon's world.[17][18]
Once players finish the expansion's story, they are awarded the option to play as an Octoling alongside Inklings in multiplayer matches.[19] The differences between the two are purely cosmetic and do not affect gameplay.[13]
Players take control of an amnesiac, unconscious Octoling who is found by the character Cap'n Cuttlefish. Cuttlefish was seeking out Agent 3, the protagonist of Splatoon, and decides to help the Octoling after hearing them humming the Squid Sisters' song "Calamari Inkantation". Cuttlefish and the Octoling are trapped in a subway-like testing facility called the Deepsea Metro, where a talking telephone identifies the player-character as "Number 10,008"; the title's verbosity prompts Cuttlefish to give them the moniker "Agent 8" instead. The Telephone informs them that to reach "the promised land", they must traverse through the Metro to collect four objects known as "thangs". Agent 8 is given assistance via radio by Pearl and Marina of the pop band Off the Hook. As Agent 8 clears tests in the underground facility, they obtain small items called "mem cakes" that serve as physical manifestations of their lost memories. After completing several test chambers and collecting all four thangs, which combine 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 rescues the duo, seemingly destroying the Telephone; Agent 3 is knocked unconscious in the process. Agent 8 then climbs through the depths of the facility towards the surface via a hole that Agent 3 left in the ceiling, while Cuttlefish stays behind to keep watch over Agent 3. Just as they are about to reach the exit, Agent 8 is confronted by Agent 3, who has been brainwashed by the Telephone with the use of a turquoise-colored, gelatinous ooze. Agent 8 defeats them in battle, freeing them from their mind control.
After reaching the surface, the trio is retrieved by Pearl and Marina. Upon their rescue, however, the facility itself begins to rise from the ocean, revealed to be an enormous statue of a human; this shocks the party, due to humans having been extinct for several millennia. From within the statue's empty eye socket, the mangled—but still functional—Telephone formally introduces itself as Commander Tartar, an artificial intelligence built by a human scientist prior to mankind's extinction from global flooding. It was programmed to encode and pass the knowledge of humanity onto the next intelligent race. While initially believing Inklings and Octarians to be this race, Tartar became personally disgusted with both their societies and instead reprogrammed itself with a new objective: to destroy all present sentient life and create a new apex species from a genetic ooze made from its past test subjects.
As it prepares to discharge an enormous solar-powered cannon from the mouth of the statue and destroy Inkopolis, Marina devises a plan to stop it from charging by covering 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, whereupon Agent 8 joins a community with both the Inklings and their fellow Octolings that had already arrived.
Development and release
Concept art of Agent 8 in a vaporwave-style location. The in-game environments of Octo Expansion were designed to appear "dated" and nostalgic to contrast with the established art styles of previous Splatoon installments.
Development of Octo Expansion began during Splatoon 2's series of free updates.[20] 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 start of Splatoon 2, as was highly requested by fans;[18] however, this was tentatively rejected as developers felt it would be jarring for Octolings to feature in a non-antagonistic role without explanation.[21] Producer Hisashi Nogami wanted to create the expansion in part to allow players to explore deeper into the series' world, and deduced that a dedicated single-player experience was the best manner of accomplishing this.[22] The assigning of players the role of an Octoling protagonist for the first time was also a means to emphasize the established differences between the Octolings' and Inklings' cultures.[23] The Octolings themselves were designed to visually contrast the Inklings by having a "rounder" appearance and a more serious disposition.[16]
The environment of a subway station was chosen out of a desire to establish a darker setting divergent from the series' otherwise cheerful art style. The Deepsea Metro was planned to have an older, dated appearance, housing characters who speak in archaic slang.[23] As with previous Splatoon games, Nogami wanted Octo Expansion's setting to feel genuine and dynamic. He explained in an interview that occasionally eliciting darker themes to offset the "bright colors and fun times" was done to make Splatoon's world better reflect reality in that "... you don't live every single day with the same attitude. You're not smiling and laughing every day of your life."[24] The Octo Expansion team sought to reinforce a "feeling of being out of place" by taking design inspiration from the cultures of "forgotten generation[s]", like those of the 1980s, that some players would be unfamiliar with, serving as an analogy for Agent 8's memory loss.[25] Examples of generational artifacts that make regular appearances include Game Boys and neon lighting fixtures.[18] Nogami wanted to further establish a mysterious atmosphere by having Octo Expansion feature non-player characters based on deep sea animals, which did not appear frequently in previous Splatoon games.[23]Toru Minegishi headed development of the expansion's deliberately minimalistic soundtrack. The songs, originally meant to be nebulous background music, were enjoyed by art director Seita Inoue to such a degree that he created a DJ character named Dedf1sh, another Octoling,[26] to act as their in-universe creator; he hoped this would increase fan interest in the songs.[16]
The level design was intended to vary wildly, and featured cut content from the base Splatoon 2 release. There were concepts for around 150 levels, but only 80 made it into the full game. The expansion's final boss, which stemmed from ideas that director Yusuke Amano had wanted to implement since the first Splatoon, was outlined in a 30-page manga illustrated by Inoue. The developers added the CQ Point system as a way to create tension and give players more agency in how they complete levels. It also served as a check-and-balance system for the expansion's "trial-and-error gameplay."[20] Some of the game's levels were designed by members of The Legend of Zelda: Breath of the Wild development team, particularly those that helped create the latter title's shrine puzzles.[27]
Octo Expansion was announced in a Nintendo Direct broadcast on March 8, 2018. The expansion was made available to pre-order shortly after its announcement, with exclusive in-game clothing items available for doing so.[28] The DLC was formally released on June 13, 2018.[29] An official CD release of the soundtrack, titled Octotune, was released on July 18.[30] An Amiibo set featuring the Octoling Girl, Boy, and Octopus was released on December 7.[31] An art book consisting mostly of concept illustrations from Octo Expansion's development, titled Inkopolis Walker, was published exclusively in Japan on December 28.[32] A physical version of Splatoon 2 with the DLC included made available on October 8, 2021, also solely in Japan.[33] On April 22, 2022, Octo Expansion was added as a benefit for the Nintendo Switch Online + Expansion Pack.[34]
Octo Expansion received "generally favorable" reviews according to the review aggregator website Metacritic;[35] it additionally garnered a score of 81.64% on GameRankings.[40] Many critics praised Octo Expansion as being of higher quality than Splatoon 2's base single-player campaign.[b]
The expansion's levels were mostly praised for their mechanical creativity, as well as their heightened difficulty. IGN reviewer Brendan Graeber praised the diversity of Octo Expansion's trials, lauding their inventive use of the Splatoon series' ink-based mechanics.[38] Similarly, Kallie Plagge of GameSpot complimented the expansion's experimentation with restricting the player to choosing a select few weapons per level. While she called the levels "great practice" for Splatoon 2's online modes, she acknowledged they could become "incredibly difficult" for those unaccustomed to said weapons.[43] The CQ Points system, which critics described as allowing less-skilled players to skip especially challenging levels, was generally praised,[15][44] though Tomas Barry of Cubed3 stated it felt needlessly complex at times.[12]Destructoid 's Chris Carter stated that while some levels were "a unique rush that fills [the player] with satisfaction for beating them", others felt tedious, with him finding the difficulty distribution inconsistent.[36] Similarly, Abram Buehner of GamingTrend found certain level types, such as the target-breaking missions, particularly frustrating. He sharply criticized the majority of the bosses for being "merely remixed" versions of fights previously seen in Splatoon 2's base single-player campaign, feeling that said bosses contrasted negatively with the expansion's otherwise creative level design.[1]
Reviewers commended the game's presentation. Alex Olney of Nintendo Life applauded the game's visuals as unique and "brimming" with intricate details, additionally lauding the soundtrack. He responded positively to the in-game cutscenes, which he stated heightened the characters' complex personalities.[18] Conversely, Chris Carter critiqued the expansion's environments as seldom feeling like a "re-skin of sorts" of Splatoon 2's base single-player, but nevertheless praised their occasional quirkiness.[36] The Deepsea Metro itself was variously described as "grungy" and "eerie";[17][45] its aesthetic deviation from the lively surface world of Splatoon 2 was seen as "refreshing" by Zhiqing Wan of Twinfinite. Brian Shea of Game Informer compared the subterranean atmosphere to that of the puzzle-platform video game Portal.[27]
Octo Expansion's narrative was warmly received. Zhiqing Wan found the speaking non-player characters likeable, and interpreted the story as an "allegory for limbo and purgatory."[45] Reviewers appreciated the expansion's story crumbs, such as the optional chat logs, that add to the overarching story of Splatoon's world, principally in relation to the Octolings.[17][46][47] The atmophere of the game's escape climax, including the final boss, was especially acclaimed by critics.[12][17][48][42] Stefan L of TheSixthAxis opined that the "tightly constructed" missions of the escape sequence serve to "expand and solidify" Octo Expansion's lore.[49] Some reviewers commented on the DLC's more overtly disturbing plot elements compared to earlier Splatoon titles,[42] with Kotaku's Ben Bertoli characterizing Commander Tartar as "genocidal" and deserving of "a spot near the top of gaming’s most hardcore villains."[50]
Legacy
The album of Octo Expansion's music, Octotune, peaked at No. 7 on the Oricon Albums Chart in Japan during the week of its debut, and outsold Splatoon 2's base game soundtrack.[51] Nintendo stated that the initial announcement of Octo Expansion preceded a sharp increase in the completion rate of Splatoon 2's regular single-player campaign.[10]
Splatoon 3, released on September 9, 2022, marks the first instance in the series where players are given the choice to be an Octoling immediately upon starting the game.[52][53] The level design and overall aesthetics of Splatoon 3's story campaign, Return of the Mammalians, were noted by reviewers as being reminiscent of Octo Expansion.[c] Certain missions from Return of the Mammalians made use of previously-seen concepts such "timed runs, target practice," with many levels being of similar difficulty to the DLC.[60] Additionally, Splatoon 3's own paid single-player expansion, titled Side Order, follows a cast of returning characters who originally starred in Octo Expansion, including Pearl, Marina, Dedf1sh, and Agent 8, the lattermost of whom the player once again assumes control.[61][62][63]
↑Parton, Mitchell (June 18, 2018). "Splatoon 2 Review – Review". Nintendo World Report. Archived from the original on May 1, 2025. Retrieved January 4, 2026.
123Kondo, Vanilla (July 21, 2018). "『スプラトゥーン2』1周年＆『オクト』配信記念！ 郷愁を誘う『オクト』の元ネタや8号とイイダの関係性など、秘話満載の濃厚インタビュー！"[Celebrating the first anniversary of "Splatoon 2" and the release of "Octo Expansion"! A deep interview packed with behind-the-scenes stories, including the origins of the nostalgic "Octo Expansion" and the relationship between Agent 8 and Marina!]. ファミ通.com (in Japanese). Archived from the original on December 27, 2025. Retrieved January 4, 2026.
↑Zawodniak, Melanie (September 13, 2022). "Splatoon 3 Review – Review". Nintendo World Report. Archived from the original on April 30, 2025. Retrieved January 5, 2026.
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