History Series / KamenRiderZiO

** In #5, Woz tells Sougo that the Another Fourze incident started with "a shooting star". After meeting the Kamen Rider Club, Sougo assumes Ryūsei Sakuta was involved, as his given name means "shooting star", only to find out Another Faiz/Fourze and the girl he's trying to save were orphans in the [[NamesTheSame Ryūsei School]].

** Ryotaro Nogami is still active as Series/KamenRiderDenO and is currently working as part of the [[TimePolice Den-Liner Police]], continuing from the ''Climax Deka'' movie.

* GambitPileup: By the series midpoint Zi-O is essentially the story of Terminators playing chess against each other for the right to start Judgement Day.

* FullyAbsorbedFinale: While the series is one for the Heisei era of ''Kamen Riders'' as a whole, several shows that had initially ended on notes ranging from {{Downer|ending}} to {{Bittersweet|ending}} [[spoiler:like ''Series/KamenRiderBlade'']] get far better closure here.

* EverythingsBetterWithSpinning: The Zikū-Driver works by inserting a Ridewatch and then spinning the Driver in a full circle.

* SpiritualAntiThesis: To ''Series/KamenRiderDenO'', being a season about TimeTravel and using that to defeat the MonsterOfTheWeek in the past. However while Den-O's time travel was used to fix damages caused to the past and time, Zi-O's time travel and various other time alterations caused time to be damaged till it was [[spoiler:pretty much hell on Earth with 19 years history of enemies the Kamen Riders faced which nearly forced Decade to destroy the world]].

* WeaponOfChoice:

*** The Gaim Armor is MultiArmedAndDangerous with ''four'' Daidaimaru Z [[KatanasAreJustBetter swords]].

[[SimilarlyNamedWorks Not to be confused with]] its predecessor ''Film/KamenRiderZO'' (which is actually pronounced "Zet-Oh" (as per the Japanese pronunciation of the letter Z), while this one is "zi-oh") or its distant relative ''Series/PowerRangersZeo''.

** At the first episode, Sougo meets [[Series/KamenRiderBuild Sento Kiryu (Takumi Katsuragi) and Ryuga Banjo]] in the cafe nascita... but as Build's history is wiped because the creation of Another Build, they become fans of Taro Satou (aka the man with Sento's modified face) instead.

** #47 has this line that [[:spoiler will shock you once you watched [[Series/KamenRiderDecade Kamen Rider Decade]]...]]

** #47 has this line that [[:spoiler will shock you once you watched [[Series/KamenRiderDecade]]...]]

* ExtyYearsFromNow: The future characters' home time, 2068, is exactly fifty years from the present day.

* DarkerAndEdgier: Even more so that it's [[Series/KamenRiderDecade spiritual predeccessor]]. This series opens with a very brutal BadFuture of Oma Zi-O crushing the Resistance forces and decimating them all, with Geiz and Tsukuyomi trying to guide Sougo away from being the most vile demon king. As the show progressed, Sougo has more of his FriendlessBackground emphasized with a few episodes of Geiz and Tsukuyomi staying distant from him in favor of White Woz's side, [[spoiler:the fact that Sougo and Hiryu lost their parents in a bus crash that Swartz orchestrated,]] the ''Kiva'' tribute being much more dramatic and intense than previous tributes before it, and the Another Zi-O II three-parter has Sougo suffering from a timeline change caused by Hiryu where nearly almost everyone he knows is against him. [[spoiler:Then there's also the fact that the show's final act deals with time paradoxes that lead to monsters from all over the Heisei era with the risk of breaking reality and unlike previous final battles, the climax of Sougo's involves him becoming Oma Zi-O over grief of Geiz dying to save him and then tearfully finishing Swartz after the latter also kills Tsukuyomi.]]

Arriving into the year 2018, they locate the younger version of Ōma Zi-O as described in their history books: an [[OrdinaryHighSchoolStudent ordinary and naive eighteen-year old]] named Sōgo Tokiwa who childishly dreams of becoming "a king" that can bring happiness to the world. One of the Resistance members (Geiz Myōkōin, ''aka'' [[TheLancer Kamen Rider Geiz]]) is insistent on completing the assassination, but the other (Tsukuyomi) begins to question if the pure-hearted Sōgo is ''really'' capable of growing up into the tyrannical Ōma Zi-O.

As Sōgo claims the power of Kamen Rider Zi-O and embarks on the road to ascension, the history of the Kamen Riders begins to distort as various parties aim to twist the future to their advantage. A mysterious group of time-travelers named the Time Jackers begin to steal the power of the Kamen Riders, creating their own [[EvilKnockoff Another Riders]] as candidates to usurp Ōma Zi-O as the Overlord of Time. A sycophantic "prophet" of Ōma Zi-O named Woz arrives from the future to ensure the ascension of his master as history dictates. And standing beside Sōgo are Tsukuyomi and Geiz, carefully watching his actions with a hand on their weapons. Will Sōgo create an unexpected destiny as "[[BigGood the most beloved and kind Overlord in history]]", or [[HitlersTimeTravelExemptionAct is he fated to become the ultimate evil]]?

%%* ''Kamen Rider Zi-O: Transformation Lessons'', a web series showcasing the riders' transformations.

** ''Rider Time: Series/KamenRiderRyuki'', written by [[Series/KamenRiderAgito veteran]] [[Series/KamenRiderFaiz writer]] Toshiki Inoue, detailing Sōgo and Geiz aiding Shinji Kido and Ren Akiyama in stopping a new Rider War.
** ''Rider Time: Series/KamenRiderDecade vs. Zi-O: Decade's Death Game'' and ''Rider Time: Kamen Rider Zi-O vs. Decade: Seven Zi-Os'', set after the series and released simultaneously. While Decade and Diend were major supporting characters during the show's final arc, these are full-fledged crossovers between the two series. [[spoiler: This also serves as the GrandFinale for both shows.]]

** The Zikū-Driver (Spacetime-Driver), used by both Zi-O and Geiz [[spoiler: as well as Tsukuyomi/Alpina]], is the main transformation device, while forms are changed with Ridewatches (similar to Decade's Rider Cards). Similar to the Drivers in ''Ex-Aid'', it has two slots for Watches, with one used for the personal transformation and the second for power-ups.

** Episode 37 hints and episode 38 outright states that ''Series/KamenRiderKabuto'' happened in an alternative timeline and currently the Kabuto timeline and the Zi-O timeline are mixing for some reason, causing time-space distortions.
*** [[spoiler: Tsukasa reveals in episode 48 that just like [[Series/KamenRiderDecade his premise]], ''all'' Kamen Riders originate from different timelines/Worlds. However due to Swartz turning Sougo into a DoomMagnet, Sougo subconsciously pulls their timelines into his in order to meet them to obtain their powers. Eventually as Sougo has obtained all of them, [[AllAccordingToPlan all the Kamen Riders' timelines have effectively merged into a single world]], allowing Swartz to execute the final stages of his MasterPlan to destroy the combined world.]]
** Episode 43 reveals that [[spoiler:Swartz and Tsukuyomi are from a different timeline than the show. Swartz arriving here for his plan while Tsukuyomi was sent to a different timeline in an attempt to kill her by Swartz and just so happened to arrived in this timeline.]]

** ''Supplementary Plans'' Episode 15.5 continues the gag in an imaginary trailer for "Kamen Rider Tsukuyomi"; while we don't see her actual Rider suit, the Ridewatch shows that her visor uses English letters but can only fit part of the name ("TSUKU") on the helmet. [[spoiler:In episode 48 we finally get to see Kamen Rider Tsukoyomi; her helmet has the word "Rider" in katakana like everyone else.]]

* ChekhovsBoomerang: In the first part of the show, Sougo has to give blank Ridewatches to Legend Riders in the past so that they absorb part of the Riders' power and transform into Legend Ridewatches by the time Sougo needs them. This concept was dropped as the story progressed, being {{Handwave}}d as a result of changes to the timeline. [[spoiler:It comes back in a big way in the final arc: Sougo travels to 2068, specifically arriving during the events of Episode 1, just before Ohma Zi-O curb-stomps the Resistance and inspires Geiz and Tsukuyomi to go back in time in the first place. He secretly slips a Blank Watch into Tsukuyomi's pocket, and by the time he returns to 2019 for the final battle with Swartz, it's transformed into a Ridewatch that lets Tsukuyomi become a Kamen Rider in her own right.]]
* ChekhovsGun: Tsukasa's contingency plan to restore his powers from his Ridewatch after Swartz stole his powers becomes significantly more important when it was shown that [[spoiler: the same plan was later used for ''Tsukuyomi'' in light of Swartz also stealing her powers, allowing her to restore her own powers with the additional benefit of turning her into a Kamen Rider.]]

** Justified with the Ziku-Driver itself. In Episode 16 Geiz destroys Sougo's Driver (at his request), but Woz [[CrazyPrepared anticipated that this might happen and created a "backup" Driver]].

** At the first episode, Sougo meets [[Series/KamenRiderBuild Sento Kiryu (Takumi Katsuragi) and Ryuga Banjou]] in the cafe nascita... but as Build's history is wiped because the creation of Another Build, they become fans of Satou Tarou (aka the man with Sento's modified face) instead.

** [[Series/KamenRiderFaiz Takumi Inui]] still works with the ''Kikuchi Dry Cleaners'' laundry service.

** [[Series/KamenRiderExAid Kuroto Dan]] still works under his father Masamune in Genm Corp, suffering writer's block due to stress from living up to him [[spoiler: that ended up being his motive for killing him.]]

** [[Series/KamenRiderGhost Takeru Tenkuuji]] is still living at Daitenku Temple, investigating supernatural phenomena with his friends Shibuya and Narita.

** At episode 21, it is revealed that ORE Journal from ''Series/KamenRiderRyuki'' is closed because of social media's influence.

** At the ending of ''Series/KamenRiderAgito'', Shouichi Tsugami opened his own restaurant. In Zi-O, he travels to France to learn about cooking, leaving Mana Kazaya as the owner. Takahiro Oomuro is a captain in the police force now, leading the resurrected G3 unit.

* DarkerAndEdgier: Even more so that it's [[Series/KamenRiderDecade spiritual predeccessor]]. This series opens with a very brutal BadFuture of Oma Zi-O crushing the Resistance forces and decimating them all, with Geiz and Tsukuyomi trying to guide away from being the most vile demon king. As the show progressed, Sougo has more of his FriendlessBackground emphasized with a few episodes of Geiz and Tsukuyomi staying distant from him in favor of White Woz's side, [[spoiler:the fact that Sougo and Hiryu lost their parents in a bus crash that Swartz orchestrated,]] the ''Kiva'' tribute being much more dramatic and intense than previous tributes before it, and the Another Zi-O II three-parter has Sougo suffering from a timeline change caused by Hiryu where nearly almost everyone he knows is against him. [[spoiler:Then there's also the fact that the show's final act deals with time paradoxes that lead to monsters from all over the Heisei era with the risk of breaking reality and unlike previous final battles, the climax of Sougo's involves him becoming Oma Zi-O over grief of Geiz dying to save him and then tearfully finishing Swartz after the latter also kills Tsukuyomi.]]

** The changes to Sento and Ryuga's personalities are drastic and played primarily for comedy. All future returning Riders remain heroic figures even without their powers, and are mostly the same in terms of personality (with the notable exception of [[Series/KamenRiderFaiz Kusaka]], who is less of an ass in this timeline.)

** Zi-O's Time Mazine mecha has a large ロボ[[note]]robo[[/note]] plastered on its torso. Geiz's is labeled ろぼ, the same in hiragana. Seemingly lampshaded in Episode 1, where Sougo incredulously says "'Robo'?" when Geiz's Time Mazine appears in front of him.

** Swartz's statement to Woz that [[spoiler:he and Tsukuyomi are cut from the same cloth is revealed he was being literal; they're siblings as shown in episode 38.]]
** Tsukuyomi [[spoiler:being from another timeline is hinted when she and Tsukasa visit her past in episode 38 and they see her childhood home is a huge house in 2058. Tsukuyomi said the remaining people still alive under Oma Zi-O's rule, live in refugee camps which makes it odd that Tsukuyomi's family alone is living in luxury.]]
** After the [=DenLiner=] crashes, forcing the Taros to interact with the heroes in episode 39 Ora wonders why is it that Zi-O seems to draw in the various Kamen Riders. [[spoiler:Episode 48 reveals that Sougo is an actual DoomMagnet set up by Swartz to pull in the various Riders and their timelines.]]

* FromBadToWorse: The final arc is pretty much a series of the heroes managing to resolve one horrible event only for an even worse situation to rear its head before they can even catch a break. [[spoiler: First, Sougo gets RetGone, and Hiryu returns, more powerful than before, and becomes an even ''worse'' Oma Zi-O. Then, it's revealed that the whole thing was bait to lure Tsukasa into a trap so that Swartz can steal his powers to become Another Decade, who promptly starts using his powers to abduct innocents to fuel an army of Dark Riders. Then the slow-burning TimeCrash that's been going on throughout the show hits full stride, causing an outbreak of monsters from all across Heisei Kamen Rider History, and threatening to break reality unless something is done about it. And Tsukasa is thinking that "something" is destroying the world to protect the rest of TheMultiverse from the potential fallout.]]

** While collecting the Legend Ridewatches was seemingly dropped due to Sougo gaining greater powers that rendered their use obsolete, episode 30 reveals that his ongoing ascension to Oma Zi-O still required him to collect ''all 20 Ridewatches'' aside from Zi-O II's power, foreshadowing tribute arcs for the last six Ridewatches to obtain. And they ''mean'' it, as when Sougo does get all 20, he finds that [[spoiler:the Drive Watch doesn't count since Geiz stole it from Oma Zi-O before the series began; Sougo needs to get his own]].

** Episode 4.5 emphasizes this by pointing out that non-Rider Hiiro Kagami is almost identical. Some of the other Riders are changed more though, such as Kaixa [[spoiler: being alive]].

** Also averted in Episode 15, where Sougo comes face-to-face with himself in 2068, confirming that Ōma Zi-O really is him.
** Episode 38 has Tsukuyomi meeting [[spoiler:her child self due to Tsukasa taking them back to 2058.]]
* NewspaperDating: In Episode 1, Sougo checks the expiration date on a milk carton Banjou is drinking from to confirm that he's really gone back to 2017.

* PietaPlagiarism: In episode 22, [[spoiler:Tsukuyomi holds Geiz in this pose after he kills himself with a Time Burst against Another Ryuga. White Woz shouting "My savior!" drives it home double]].

** In Episode 5 Woz tells Sougo that the Another Fourze incident started with "a shooting star". After meeting the Kamen Rider Club, Sougo assumes Ryūsei Sakuta was involved, as his given name means "shooting star", only to find out Another Faiz/Fourze and the girl he's trying to save were orphans in the [[NamesTheSame Ryūsei School]].
** In episode 9, Another OOO/Kuroto Dan drops a Genm Ridewatch which Geiz and Tsukuyomi picked up. Assuming his cracked origin year display read "2016", the same year indicated on the Ridewatch, they travel to 2016 to defeat him using Genm's powers. This ended in a failed attempt where Tsukuyomi realizes Another OOO's year display actually reads ''2010'', which meant that the Genm Ridewatch they obtained [[MundaneUtility was not what they needed.]]

** When the cast asks Woz why Geiz's name is based on "gates" and not "gate" in Episode 2.5, he tries to make the excuse that it makes Geiz sound rich, like a millionaire; referring to the tech mogul Bill Gates. This is also why Geiz's new form from the Hyper Battle DVD is officially transliterated as Bibill Geiz, which is lampshaded immediately afterward.

** Episode 6.5 openly names ''Film/{{Bleach}}'' as the reason why neither Fourze or Meteor returned for guest appearances.
** In episode 11, Swartz thought Geiz [[WesternAnimation/TheTransformersTheMovie was made of sterner stuff]].

** In episode 16, Heure [[Series/IronChef carefully picks up a yellow bell pepper before taking a bite with a grin.]] He even does the overdramatic flourish as he does it.

** Episode 20's title is [[Series/WhoWantsToBeAMillionaire "Final Answer?"]].

* TakesOneToKillOne: One of the rules presented in Episodes 2.5 (to the audience) and 4 (to the characters) is that "An Another Rider can only be defeated by the same Rider's powers". However, since the Another Riders' existence negates the powers of the original Riders, this pretty much means that only Zi-O or Geiz can do the job once they get the appropriate Legend Rider Ridewatch. Eventually, this rule gets broken as our heroes' upgrades can simply overpower the Another Riders without needing to match the powersets.

** The later half of the show starts to see reality break down in the face of so many paradoxes. Another Riders start co-existing with the actual Kamen Riders, alternate timelines start merging into Zi-O's timeline, and at one point [[spoiler: Sougo is RetGone, causing Hiryu to become an ''even worse'' Oma Zi-O]]. While the heroes intially don't seem to care too much about the cause at first, other parties show up to try and get rid of the source. [[spoiler: Michal blames Tsukuyomi and Geiz for trying to change the past (in addition to the former being from another timeline entirely), while Tsukasa theorizes that Sougo is the source and that he might have to destroy the World of Zi-O before the distortions get out of hand.]]

* TimeCrash: The second half of the show is essentially a slow-moving example, as the paradoxes created by all the various time travelers begin building up to the point of causing damage to the fabric of time itself. This leads to breakdowns of the pre-existing rules, multiple inconsistent timelines coexisting, and even events happening completely out of order. [[spoiler:And yet ''even this'' is part of the StableTimeLoop that Swartz created. In episode 47 we see the full result as the various Rider histories are fusing with Sougo's world such as various structures from their histories like the [[Series/KamenRiderBuild Skywall]], [[Series/KamenRiderDouble Fuuto Tower]] and [[Series/KamenRiderGaim Yggdrasill Tower]] appearing. This also results in the various monsters from those histories being summoned and terrorizing the public]].

** Episode 12, the ending of the Gaim arc, reveals that for the first time, something has happened that wasn't according to Woz's record of the future. This establishes that the show up until now has been enacting a StableTimeLoop, and therefore that Geiz and Tsukuyomi are actually on the path to ''causing'' the birth of Oma Zi-O by going back in time to try and stop it.
** Episode 15 demonstrates TheUntwist in splendid fashion. The show up to that point has had Sougo fervently disbelieve that he could ever become Oma Zi-O, and he's so different from his future counterpart that Geiz, Tsukuyomi, and even much of the audience expected it to be revealed that he'd been framed, especially after Ex-Aid and Build both had premise-shattering reveals at this point of their respective runs. Instead, the twist is that there is ''no twist'', as Sougo is at last forced to confront the horrifying reality that he truly is Oma Zi-O.
** Episode 27 reveals that Swartz [[spoiler:not only orchestrated the bus crash that killed Sougo's parents ten years ago, but he's also behind Sougo's desire to be king, bringing all the children from that bus to the Day of Oma to see who had the ability to become Zi-O. This also explains why he just shoves Another Watches into random people instead of scouting them like his two allies. '''He already HAS his candidate for king, and he always did.''']]
** Episode 46 sees Swartz finally lay out his XanatosGambit for Sougo, and how thoroughly Sougo has been manipulated for his entire life. [[spoiler:His only real friends are time travelers from timelines that are mutually incompatible with his own, and the only timeline in which they all coexist is the one that brought them together to try and kill him. For Sougo's friends to live, he must become [[ProtagonistJourneyToVillain Oma Zi-O]].]]
** Episode 47 has things go FromBadToWorse. [[spoiler: Reality finally starts collapsing under all the time paradoxes, causing the Ridewatches to break, alternate worlds to start merging together, and monsters from all across Heisei Kamen Rider history to start showing up and terrorize the people. As a result, Tsukasa decides that he needs to destroy the world.]]

** In Episode 15, Sougo reveals that [[spoiler:ever since he was a child, he had a dream about giant robots destroying the city, people dying left and right, and a mysterious man telling him to become a king so he could save the world. After Tsukasa flings him fifty years into the future, Sougo meets a man who introduces himself by describing the exact same dream, revealing himself as Sougo's future self and Ōma Zi-O.]]

** Black Woz's investigation of the fateful bus accident that Sougo and Hiryu were in ten years ago reveals that [[spoiler: the listed driver for that bus is '''Tsukasa Kadoya''']].
** Episode 30. Daiki[=/=]Diend's real target was [[spoiler:White Woz's reality-rewriter tablet]], and he finally reveals his accomplice behind one of those shimmery portals from ''Decade''. Except it's not anyone from that series. [[spoiler:It's Oma Zi-O.]]
** Episode 43. Diend freezes time, allowing Swartz to come over [[spoiler:and take Decade's power, finally able to obtain the power of Another Decade.]]

* AnimatedActors: A live-action version. The ''Supplementary Plan'' episodes operate on a bizarre level of reality in between MediumAwareness and NoFourthWall, where the cast are fully aware that they're fictional characters and make reference to Toei, toy companies, specific writers and directors, and at one point they even spin the camera around to show the production crew...but they're still the fictional characters rather than the actors. Episode 10.5 ends with Geiz flubbing and referring to Sougo as "Okuno-kun", which prompts the director to call "Cut!" and Sougo to gently tease "You can't do that!"
* AscendedMeme: 14.5 has Sougo, Geiz, Woz, and Tsukuyomi shout "Onore Dikeido!" to Tsukasa at the end of the episode.
* BellisariosMaxim: [[InvokedTrope Invoked]] as one of the rules of the World of Zi-O, as explained in episode 2.5. When Ryuga asks about inconsistencies in ''Build''[='s=] altered timeline, Sento replies that one of the rules of time travel is "Don't ask unnecessary questions about adult circumstances." Geiz brings it up again in Episode 13.5 when Takeru uses a hand puppet of Yurusen, presumably referencing the fact that neither the character nor her voice actress Creator/AoiYuuki came back for ''Zi-O''.
* BlatantLies: In Episode 6.5, [[Series/KamenRider555 Takumi and Kusaka]] try to give explanations why combining the ''Fourze'' and ''555'' tributes are a natural fit, such as Fourze's limb symbols being an intentional tribute to the ''555'' Riders (which falls apart because Fourze has a fourth square symbol that doesn't match anyone) or both shows and ''Zi-O'' being about kings (''555'' involves hunting for an Orphnoch King, while ''Fourze''... has an "oh" ("king") sound in his name). [[note]]The real reason was much more mundane - 4 is followed by 5. Also, the space theme of Fourze gave a solution Faiz's Worms invading.[[/note]]

** Heard in Episode 6.5, which discusses the ''Fourze'' actors being unavailable. Sōta Fukushi and Ryō Yoshizawa's names, plus the title "Film/{{Bleach}}" are bleeped ''just'' enough to cover Toei legally. Spoofed at the end of the segment when they discuss Shinichirō Shirakura, producer for both ''Zi-O'' and ''555'' (among other ''Rider'' series): he's called "Shirakura-P"[[note]]a common Japanese nickname for producers[[/note]] but the bleep comes ''after'' the P, meaning it doesn't actually censor anything at all.
** It's used again in 11.5, to cover Tsukuyomi when she references ''Manga/{{Doraemon}}''.
** And again in 13.5, first when Tsukuyomi compares Yurusen to a character from ''Manga/GeGeGeNoKitaro'', and again when Sougo compares ''Ghost'''s "collect 15 Eyecons to get a wish" plot to ''Manga/DragonBall''. Geiz then tells him that if they keep referencing Magazine/ShonenJump properties like ''Bleach'' and ''Dragon Ball'' it'll just get bleeped out...[[HypocriticalHumor and Sougo points out that his rant is gonna get bleeped too]].
* BriefAccentImitation: In 13.5, Tsukuyomi dreamily asks if "the Nation's Boyfriend" (''Series/KamenRiderDrive'' star Ryoma Takeuchi) will be appearing in the show. Takeru drops into an impression of Takeuchi as Shinnosuke Tomari, even referring to Tsukuyomi as Kiriko, and basically tells her "don't ask too many questions about it".
* DependingOnTheWriter: Lampshaded in 10.5, where the characters complain that their characterization seems off and realize that a different writer had come in on the last couple episodes. And that the director didn't keep things straight because, looking forward through episode 12 and ''Heisei Generations Forever'', there have been ''seven'' directors already. Sougo concludes that it's up to the cast to protect their own characterization if the staff won't.
* FoilerFootage: Discussed InUniverse in Episode 16.5. Sougo, Geiz, and Tsukuyomi wonder how Toei managed to keep the "big secret" of ''Heisei Generations FOREVER'' (namely, Takeru Satoh reprising his role as [[Series/KamenRiderDenO Ryotaro Nogami]] for the first time in ten years) from being spoiled. Woz explains that the producers used a few tricks, like leaving those scenes out of the shooting script (marking them with "To Be Added") and filming in secret with a skeleton crew on days where no filming was scheduled[[note]]For example, on days that were set aside in case regular filming was rained out[[/note]]. The three heroes remark that they didn't even realize what was happening and actually get offended that Toei would freeze them out like that.
* FreezeFrameBonus: Episode 11.5 reveals that there are a number of items taken from past ''Rider'' series scattered around the Kujigojido shop. The cast specifically points out a science-themed clock from ''Build'' and challenges viewers to find the rest.
* FutureSlang: Spoofed in Episode 15.5, where Tsukuyomi refers to Sougo as "basic", followed by a pop-up window that explains we aren't really sure if they still use 2010s slang in 2068.
* HostileShowTakeover: In Episode 15.5, Sougo explains that he can't give up his belt because he's the star of the show. Geiz then reveals that he ''wants'' this to happen, so the show can be replaced by "Kamen Rider Geiz", complete with a debut trailer. Tsukuyomi follows up with a trailer for "Kamen Rider Tsukuyomi".
* MeaningfulName: Episode 1.5 explains the names of the main trio:

** Tsukuyomi is named after the [[Myth/JapaneseMythology goddess]]. However, the name can also be read as "counting moons", in other words, a way of telling time. It also means "moon phase", which becomes more relevant later on [[spoiler: since her actual Rider form has a crescent moon motif in the mask]].

* MerchandiseDriven: Specifically addressed in Episode 9.5. Sougo asks why [[Series/KamenRiderExAid Kuroto Dan]] is in the ''Series/KamenRiderOOO'' arc and initially concludes that it's because of the toy releases[[note]]The limited-time offer for the Genm Ridewatch started on November 3rd 2018, in the middle of the OOO arc[[/note]] and wonders if that means the entire series is at the beck and call of toymakers. However, Woz and Kuroto explain that it's the other way around and that merchandise release dates get shifted around in order to line up with the episode airdates.[[note]]The specific example given is the second wave of ''OOO''-themed toys, which came out on November 10th, the airdate of Episode 10[[/note]] In reality, the reason for Kuroto's appearance was because it was the only time actor Tetsuya Iwanaga was free to record his cameo.

* OutOfCharacterMoment: In Episode 15.5, Geiz complains about how the ''Supplementary Plans'' episodes will make him say things that he would never say normally, like the suggestion of blowing up Toei Studio back in Episode 3.5.

** After Hora claims in episode 3.5 that there's going to be a Rider War to determine the new king, the main trio go this route to try and prevent it. Tsukuyomi proposes simply appealing to the writers, while Geiz wants to kill the producers. Sougo takes it a step further and proposes ''destroying Toei studio''.
** Episode 6.5 has Kusaka blame producer Shirakura for the awkwardness of how the ''Fourze'' and ''555'' tributes were mashed together.
** Episode 7.5 has the main characters complain that many of the scenes that they shot ended up not going into the final product and/or were cut out. Sougo decides to confront the directors himself. The result? ''The entire premise of Sougo becoming Oma Zi-O was cut out''.
** In 10.5 the main characters express frustration with the staff for not being able to keep their characterizations straight.
* RedHerring: Episode 3.5 claims that the series is heading for a BigBadassBattleSequence where all 20 Heisei Riders were going to fight it out for the right to become king. This never happens, nor is it even ''hinted'' to happen in the series itself.

* TheUnReveal: In Episode 15.5, the "Kamen Rider Tsukuyomi" trailer gets shoved away by Sougo ''just'' before it would have revealed what Tsukuyomi's rider costume looked like. When she's introduced in the show proper, her watch, mask, and ''color scheme'' are all different than what was shown in the Supplementary Plan, meaning the alternate design teased there never got a reveal at all.

* ''Kamen Rider Heisei Generations FOREVER'', the annual crossover movie teaming Zi-O with Series/KamenRiderBuild.

!!''Kamen Rider Zi-O'' provides examples of:

* SocietyMarchesOn: They get anvilicious with this in the ''Series/KamenRiderRyuki'' arc - thanks to the spread of social media, ORE Journal has been rendered defunct and ultimately shut down by present day.

** ''Rider Time: Series/KamenRiderDecade vs. Zi-O: Decade's Death Game'' and ''Rider Time: Kamen Rider Zi-O vs. Decade: Seven Zi-Os'', set after the series and released simultaneously. While Decade and Diend were major supporting characters during the show's final arc, these are full-fledged crossovers between the two series.

* FakeBetterAlternateTimeline: White Woz comes from an alternate timeline to the future of Oma Zi-O, where Geiz Revive defeated Zi-O before he could become Oma and apparently changed the world for the better. [[spoiler:However, it's eventually heavily {{implied}} that life ceased to exist altogether in that timeline, making it much worse than the already BadFuture of Oma Zi-O's rule.]]

* RealityEnsues:
** While Sougo dreams of being king, no one other than Geiz and Tsukuyomi takes him seriously, usually telling him to pursue something more grounded in reality.
** After the rise of social media, [[Series/KamenRiderRyuki the ORE Journal]] was rendered obsolete and ended up going out of business.
** Hayase (Another Wizard) doesn't end up with Kaori just because he came clean with her about his feelings and everything. (Granted that happened in ''Series/KamenRiderKiva'', but not here...)

* {{Deuteragonist}}: Geiz and Tsukuyomi share the position with Geiz having more focus in the first half of the series while the second half focuses more on Tsukuyomi.

* MythologyGag:
** Many of the clocks and knick-knacks in Junichiro's shop are props that were used in previous seasons. Some were not the exact piece used, but are of the same model and appearance.
** Zi-O's name calls back to both the last 20th anniversary Rider ([[Film/KamenRiderZO ZO]]) and the last time travel Rider ([[Series/KamenRiderDenO Den-O]]).
** Zi-O was born in 2000, the year ''Series/KamenRiderKuuga'' premiered and started the franchise's Heisei era.
** The naming scheme for the Another Riders is the same as that of [[Series/KamenRiderAgito Another Agito]]. The Another Rider for Agito turns out to be a particularly twisted mythology gag - while certain humans could potentially evolve into Agito, Another Agito only existed because the real form of Agito was taken by Shoichi Tsugami [[spoiler:and his sister before that]]. In ''Zi-O'', humans are forcefully evolved into Another Agitoes ''whether they want to or not.''
** During Woz's opening and ending narration (from Episode 2 onwards), [[Series/KamenRiderExAid Cronus's]] clock can be seen behind him.
** Two relating to Ōma Zi-O:
*** His "Rider/ライダー" visor is vaguely shaped like a bird similar to [[Series/KamenRider Shocker]]'s symbol.
*** Him being an evil version of [[TheProtagonist Sougo]] who [[EvilOverlord becomes a Demon King]] in a BadFuture makes him similar with Future!Kotaro Minami in the {{manga}} adaptation of ''Series/KamenRiderBlack''.
** In a FreezeFrameBonus, [[CreepyDoll Dr. Maki's doll]] can be seen in the background of a few of Kuroto Dan's scenes during the OOO arc.
** The three Riders in the ''Over Quartzer'' movie are homages to Heisei-but-not-Heisei Riders -- that is, series that aired in Japan's Heisei era, but aren't counted in the franchise's Heisei group. One is based on ''[[Series/KamenRiderBlackRX Black RX]]''; the second is a shared reference to ''[[Film/ShinKamenRiderPrologue Shin]]'', ''[[Film/KamenRiderZO ZO]]'', and ''[[Film/KamenRiderJ J]]''; and the third homages ''[[Series/KamenRiderAmazons Amazons]]''. The movie also features cameos from a variety of other works outside the main series, including the ''[[Series/KamenRiderGaim Kamen Rider Zangetsu]]'' stage show, ''[[Series/KamenRiderDrive Kamen Rider Brain]]'', ''[[Recap/KamenRiderExAidKamenSentaiGorider Kamen Sentai Gorider]]'', ''Film/KamenRiderG'', the [[Manga/KamenRiderKuuga manga version of Kuuga]], and even an unofficial parody ''Kamen Norider''!
** Another Kabuto's belt buckle is a yellow larva with red markings curled into a ball, which evokes the design of Series/KamenRiderStronger's Electrer belt; Kabuto was specifically designed to be an homage to Stronger.
** Sougo's former classmate Owada is effectively a [[Series/KamenRiderExAid gender-flipped Nico Saiba]].
** [[spoiler:Kamen Rider Tsukuyomi]]'s design and henshin pose is one to [[Series/KamenRiderRyuki Miho Kirishima/Kamen Rider Femme's]]. Her crescent moon-shaped visor is also reminiscent of [[Series/KamenRiderGaim Zangetsu's]].
** A good chunk of the basis of ''Kamen Rider: Bibibi no Bibill Geiz'' comes from ''VideoGame/CorpseParty'' or possibly ''Anime/GhostStories''.[[labelnote:*]]''Ghost Stories'' was considered infamously subpar by anime standards, and the American GagDub came as a result of it being forced into a package deal to make ''some'' kind of money off of it. The Gag Dub proved much more popular, even with the original creators.[[/labelnote]]