OOO, Den-O, All Riders: Let's Go Kamen Riders (オーズ・電王・オールライダー レッツゴー仮面ライダー Ōzu Den'ō Ōru Raidā: Rettsu Gō Kamen Raidā) is a film released on April 1, 2011, to commemorate the 40th anniversary of the Kamen Rider Series. The catchphrase for the movie is "The world, these are Japan's heroes!!" (世界よ、これが日本のヒーローだ!! Sekai yo, kore ga nihon no hīrō da!! ). While the film will feature all of the franchise's protagonists, the main heroes of the original Kamen Rider (#1), Kamen Rider Den-O, and Kamen Rider OOO will be the main characters. The film's subtitle "Let's Go Kamen Riders" is an homage to the theme song of the original series, "Let's Go!! Rider Kick" (レッツゴー！！ライダーキック Rettsu Gō!! Raidā Kikku ). The film also marks the 60th Anniversary of the Toei Company and to commemorate it, the film features characters from other works of Shotaro Ishinomori: Kikaider, Kikaider 01, Inazuman, and Zubat.
The course of history is accidentally changed when Ankh leaves behind an O Medal in the past after Kamen Rider OOO helps Den-O and New Den-O chase a Mole Imagin all the way back to November 11, 1971. When they return to the present time on April 1, 2011, they discover that Shocker succeeded in conquering the world and now Kamen Rider #1 and #2 are Shocker's top agents. In order to defeat Shocker, Kamen Rider OOO and the Den-Liner gang must travel back in time to gather other Kamen Riders to defeat Shocker and restore the proper timeline.