! Spoilers for all preceding ''Franchise/KamenRider'' entries, including ''Series/KamenRiderW'', will be left unmarked ahead. Administrivia/YouHaveBeenWarned!

[[quoteright:350:https://static.tvtropes.org/pmwiki/pub/images/lets_go_kamen_riders.jpg]]

''[[Series/KamenRiderOOO OOO]], [[Series/KamenRiderDenO Den-O]], [[MassiveMultiplayerCrossover All Riders]]: Let's Go Kamen Riders'' is 40th anniversary movie of the ''Franchise/KamenRider'' franchise. Premiered in Japanese theatres on April 1, 2011.

After Ankh accidentally coughs up a Cell Medal in the past while travelling with New Den-O, Shocker uses the technology to create a new Kaijin that manages to defeat [[Series/KamenRider the original Double Riders]]. Due to this, the past is rewritten so that Shocker now rules the world, and all the other Riders cease to exist. It's up to the Kamen Riders OOO, Den-O and New Den-O, accompanied by Ankh, to fix the mess they caused and save all of humanity.

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!! This movie contains examples of the following tropes:

* AdaptationalBadass: [[spoiler:The Great Leader's original incarnation didn't put up much of a fight. This one takes all of the Riders to finally put down.]]
* AdaptationalHeroism: When the secondary Riders show up for the All Rider Break, some of them are from ''Ryuki,'' which means a ''lot'' of them aren't the "team up and take on an EvilOverlord" type. We're lookin' at ''you,'' [[AxCrazy Takeshi]] [[BloodKnight Asakura]] (though by no means ''only'' at you.)
* ArcNumber: 40. For this 40th anniversary film we go from 2011 to 1971 then back again. Plus the All Rider Break forms the shape of the number 40.
* AttackOfThe50FootWhatever: King Dark, naturally. [[spoiler:However, even he's dwarfed by the Great Leader's OneWingedAngel form, which destroys King Dark just by ''showing up''.]]
* BadFuture: Ankh [[NiceJobBreakingItHero unwittingly causes a]] ButterflyEffect when he gets jostled hard enough to cough up a Cell Medal while in the past with New Den-O. This Cell Medal is picked up by a Shocker goon, who then takes it to General Black. As it turns out, they had been experimenting with a reverse-engineered Core Medal. The resulting Greeed ended up defeating the Double Riders, causing a future where Shocker and other such evil organizations control the world.
* BigBad: Only the Great Leader of Shocker himself.
* BigDamnHeroes: During the battle in the present, [[spoiler:''Series/KamenRiderV3'' arrives, leading the other main Kamen Riders. When the Great Leader transforms, Kamen Rider Birth arrives, leading the Secondary Riders.]]
* CanonWelding: When [[Series/KamenRiderStronger General Shadow]] runs away, he is stopped by four other heroes. As Owner notes, "Kamen Riders aren't the only allies of justice." These four heroes are Series/{{Kikaider}}, Kikaider 01, Series/{{Inazuman}}, and Series/KaiketsuZubat, all made by Creator/ShotaroIshinomori.
* CastingGag: Tomokazu Seki, who fills in for Daisuke Ban as the voice of the tokusatsu incarnation of [[Series/AndroidKikaider Kikaider (Jiro)]], previously voiced the anime incarnation of the character in ''Anime/AndroidKikaiderTheAnimation''.
* ChekhovsGunman: The man in white who threw the OOO Driver back to Eiji.
* ChekhovsGag: At the beginning of the film, OOO fights three Imagin, believing them to be Yummy even though they don't bleed Cell Medals, but Ankh arrives and tells him they're not Yummy at all. [[spoiler:Yet Ankh was later able to procure a ''Core'' Medal from another Imagin: Momotaros.]]
* ChuckCunninghamSyndrome: [[spoiler: Both [[Series/KamenRiderAgito Another Agito]] and [[Series/KamenRiderKiva Dark Kiva]] are absent from the army of extra riders Birth summons. While it's understandable why either King[=/=]The Bat fangire or Taiga Noboru wouldn't show up as the latter (former was an outright villain, latter is already present in the army as Saga), it's not known why Otoya Kurenai isn't present, given that he isn't present in the army as Proto[=-=]Ixa, and no explanation whatsoever is apparent for why Another Agito is absent]].
** In a more minor example, there is no hint of Ryotaro and Hana, the main human characters of the original ''Den-O'' series, despite Kotaro (Ryotaro's grandson) being one of the main characters.
* ContinuityPorn: But of course. The most obscure reference is either Snack Amigo (Chiyoko's has turned into one; it was the hangout in the original series for about five episodes or so.) or Mitsuru and Naoki (names not chosen by accident; they're two kids who became ThoseTwoGuys in the last arc of the original series; apparently they were from the future all along?) Also, Nokko is named for three girls with -okko names. And of course, every monster was a MonsterOfTheWeek from a past series, some ''every'' bit as old as Snack Amigo.
* ContinuitySnarl: Somewhat unsurprising, given Yasuko Kobayashi wasn't writing this one.
** In the film, Eiji has full sets of all medals[[note]]not counting Black ones that Eiji never used, or the Future and Super ones that didn't appear until after the series[[/note]] except for Purple and Orange[[note]]the former hadn't been introduced yet, and the latter is movie-exclusive[[/note]]; Ankh's presence means that this can't take place after the series (when Eiji ''would'' have full sets of all medals), and assuming the movie is supposed to take place after episode 29 (as implied by the episodes), Eiji would have full sets of Red and Blue medals, but only 1 of all the other colors introduced in the series by that point[[note]]this makes it impossible to place at ''any'' point in the series, since he never had a complete collection of medals at any point in the series[[/note]].
** The film states it's set in November 1971, but most of the elements shown in the past (the Kamen Rider Squad, the designs of the Double Riders outfits, the fact that the Double Riders are even in the same place[[note]]At this point in the original series, Rider 1 was fighting Shocker overseas whilst Rider 2 fought in his stead in Japan.[[/note]], the outfits of the Shocker grunts, Ikadevil and Ambassador Hell are shown as resurrected despite the fact that they didn't originally die until 1972) are more consistent with elements from 1972.
** [[Series/KamenRiderV3 Kame Bazooka]] is present despite the fact that Destron wasn't created until 1973, after the defeat of Gel-Shocker. One ''could'' write that off as Shocker simply creating the monster earlier in this timeline...if it wasn't for the fact that it still has the Destron symbol on its belt.
** Eiji is able to ride his bike in the altered timeline despite the fact that there would obviously not be any Ride Vendors for him to use.
* DemotedToExtra: Being a ''Kamen Rider'' crossover movie, this applies to most returning heroes and villains beyond the stars. A notable example is [[Series/KamenRiderDecade Decade]], the recent anniversary Rider, whose appearance here has him as FakeShemp in a quick cameo like many of the past Riders.
* DemotedToDragon: All of the series' past main villains that appear here are reduced to the Great Leader's flunkies.
* DisneyDeath: [[spoiler: In short order, Teddie, Naomi, Owner, Urataros, Ryutaros and Kintaros. Who all die during the escape from the failed attempt at preventing the creation of the Shocker Greeed and only come back in the Climax once the Riders' history is restored.]]
* TheDragon: General Black to the Great Leader of Shocker.
* EleventhHourRanger: [[spoiler:[[SixthRanger Kamen Rider Birth]] [[AndTheRest and dozens of other extra riders]] suddenly arrive to back up the primary riders when the Great Leader becomes Rock Great Leader.]]
* EleventhHourSuperpower: [[spoiler: Ankh ends up being able snatch away the Core Medal that started the trouble, as well as yank a Medal from Momotaros, giving them to Eiji to become Kamen Rider OOO [=TaMaShii=] Combo.]]
* EvilVersusOblivion: One way to look at many of the villainous Riders who teamed up to defeat [[spoiler:the Great Leader. While some of them ''are'' nasties, the Great Leader is currently going OmnicidalManiac and destroying his own minions along with the heroes...]]
* TheFaceless: All FakeShemp Riders and villains of course. A notable example are Riders 1, 2 and V3, who do not appear out of their Rider forms despite being voiced by their original actors (Hiroshi Fujioka, Takeshi Sasaki and Hiroshi Miyauchi).
* FakeShemp: Inevitable, given the number of past heroes and villains going back to 1971. Aside from the main stars, almost all of the Kamen Riders appear in-costume only and voiced by replacement voice actors. It also affects many of the villains, along with the other four "allies of justice", though Creator/HiroshiMiyauchi returns to voice [[Series/KaiketsuZubat Zubat]] as well as [[Series/KamenRiderV3 V3]], and Creator/TomokazuSeki, who previously voiced Series/{{Kikaider}} in ''[[Anime/AndroidKikaiderTheAnimation Android Kikaider: The Animation]]'', voices the tokusatsu incarnation of the character here. Really, it's surprising that so many ''were'' the original actors.
* ForWantOfANail: The whole reason that the BadFuture exists is because [[spoiler: Ankh's greed in trying to get the Core Medals during 1971 when all of the other Greeed were dormant caused him to leave the Den-Liner in a hurry, causing Eiji to go after him and get into a scuffle. One of his Cell Medals dropped out during the scuffle getting picked up by a Shocker Mook who then presented it to his leaders, and thus escalated to the main plot of the movie.]]
* FreezeFrameBonus: during the All-Rider Break, it can be picked out that not every Rider is riding a motorcycle. [[spoiler:Agito's Tornador is on its HoverBoard form, what looks like Double's [=RevolGarry=] bringing up the rear, among others.]]
* GasMaskMooks: The Shocker Greeed. The gas mask is probably inspired by the look of the Shocker Soldiers in ''Film/KamenRiderTheFirst'' and ''Film/KamenRiderTheNext.''
* HeroicSacrifice: [[spoiler:Teddie stays in 1971 to save Naoki and the Kamen Rider Scouts from the Shocker monsters, dying in the process.]]
** [[spoiler:An unusual example with Naoki, who stays in 1971 to prevent the Double Riders from being fully brainwashed through TheSlowPath by becoming a Shocker Scientist and later declines to be taken back to his era.]]
* IChooseToStay: [[spoiler:A variation with Naoki, his grown-up self declines Kotaro's attempt to take his child self back to the present as not only did he prevent the Double Rider's brainwashing, but he had a fulfilling and happy life despite all the losses he had, which includes being the father of his best friend, Mitsuru.]]
* InSpiteOfANail: Despite the fact that Shocker now conquered the world in 1971, all future evil organizations and monster races still emerged, only now they have been incorporated into Shocker.
* LegionOfDoom: Not [[Series/KamenRiderDecade Dai]]-[[Film/KamenRiderDecadeAllRidersVsDaiShocker Shocker]], or [[Film/KamenRiderXKamenRiderWAndDecadeMovieWar2010 Super Shocker]]. Instead its the original Shocker, only this time its ambitions to take over the world have been more fruitful thanks to the Shocker Greeed. By 2011, their ranks consist of villains and monsters from across Kamen Rider history. Thankfully, [[spoiler:the respective riders they fought against appear to take them on once more.]]
* MascotMook: The Shocker Soldiers become this in the advertising and net movies, to the point where it's downright ''weird'' to see them trying to ''kill people'' in the actual film.
* MythologyGag
** Naoki and Mitsuru are named after boy Rider Scouts from the original series, while Shigeru is named after Shigeru Tama, the main Rider Scout from ''V3''. This gag would be repeated in ''[[Film/SuperHeroTaisenGPKamenRider3 Super Hero Taisen GP]]''.
** [[spoiler:Rock Great Leader is a beefed-up version of the Great Leader's Delza Army incarnation from the finale of ''Series/KamenRiderStronger''.]]
* OmnicidalManiac: [[spoiler:Rock Great Leader ends up destroying every member of Shocker that the heroes hadn't already killed.]]
* OneWingedAngel: [[spoiler:The Great Leader transforms into the Rock Great Leader[[note]]Ganseki Dai Shuryo[[/note]] after OOO defeats his normal form.]]
* PlotHole: A lot of plot elements are either pulled out of or disappear into nowhere, to the point where thinking about them too hard will probably make your head throb. Most jarringly is that at no point in the movie is the timeline actually fixed as the heroes desperately wanted. Shocker is defeated in the present by the Riders (Most of whom shouldn't exist in this timeline anyway), but when the credits role, the bad timeline is still the one which exists.
* TheSlowPath: [[spoiler: Naoki gets left behind in the past after the failed attempt by the Den-Liner Crew to stop the creation of the Shocker Greeed. He would grow up to become the Shocker scientist who removed the Double Riders' brainwashing, and, shockingly, his best friend's, Mitsuru, father.]]
* SuperMode: OOO's one-time Tamashii Combo allows him to defeat the Great Leader, who before then overpowered 25+ Kamen Riders.
* TemporalParadox: [[spoiler:Naoki and Mitsuru are best friends in the contemporary era, but when Naoki gets left behind in 1971, he grows up to become Mitsuru's father, which wouldn't have been possible if they weren't friends in the first place.]]
* TimeyWimeyBall: [[spoiler:A change in history allowing Shocker to conquer the world in 1971 results in all Riders after the original two being apparently erased from existence, with the exception of those aboard the DenLiner. However, they all spontaneously reappear to fight Shocker in 2011. Owner's explanation is that they are here because they were not erased from the memories of the people.]]
* ATwinkleInTheSky: OOO does this to [[spoiler:the Great Leader.]]
* VillainDecay: Somewhat inverted for the Shocker Combatmen. While they're still mooks to be mowed down ''en masse'' by our heroes, they're far more sinister than before, to the point that they outright kill people during the movie.
* TheWorfEffect: [[spoiler:The Shocker Greed is shown to be powerful enough to defeat the [[Series/KamenRider Double Riders]] easily.]]
** [[spoiler:Gets on the receiving end later when they have their rematch in the present. With him going down in 2 hits.]]
** [[spoiler:General Black gets easily killed by OOO in the present.]]
** [[spoiler:The Great Leader kills King Dark, Darom, Apollo Geist and General Jark just by appearing and causing them to fall into a crack on the ground.]]
* YouAreNotAlone: [[spoiler:All of the previous main Kamen Riders arrive to assist New Den-O, OOO and the Double Riders when they find themselves overwhelmed by Shocker's troops.]]
--> [[spoiler:"It's not just four Kamen Riders!"]]