Development Gag: The Evol Driver has unused sounds for Evol Lock (the abiotic Best Match for the Dragon Fullbottle), Evol Tank, and Evol Dinosaur (in relation to the scrapped Kyoryu Fullbottle), suggesting they were planned to be made/used but scrapped. Evolt implicitly references Evol Tank in particular when he receives the Evol Rabbit Evolbottle after possessing Sento, being visibly disappointed by the outcome.
Enforced Method Acting: As the Cerebus Syndrome kicks in and things get more tragic, Sento’s appearance shows visible signs of exhaustion from all the heavy conflict. Reportedly, the real reason Sento looks so tired is because Atsuhiro Inukai would stay up late at night playing Monster Hunter.
God Never Said That: When Kamen Rider Build: Be The One was stated to happen after the Japanese Civil War. It caused many people and sources to think and outright state that the movie took place after the series. However, not long after its announcement #42 aired and has Evolt destroys the Touto government thus ending the civil war in Seito's victory.
Meme Acknowledgement: The final episode nods to a couple of the show's more popular memes: In the new world, Taro Satou is a famous rockstar while Sento Kiryu is literally unknown. Soichi and Misora (who are fans of Taro's) quote his memetic "We're having yakiniku tonight!" Meanwhile, Utsumi (who's working in a factory) tries to snap a metal bar over his knee like he did Namba's cane...it doesn't go so well for him this time around.
Atsuhiro Inukai, Sento’s actor, mentioned at a press conference that he watched Kamen Rider Kabuto when he was in middle school.
Eiji Akaso, who plays Ryuga Banjo, has said that his favorite Rider is Kuuga and his grandfather once gave him a toy Arcle for his birthday.
Yukari Taki, the actress for Sawa Takigawa, has expressed that her favorite Shōwa and Heisei Riders respectively are Kamen Rider V3 and Kamen Rider Accel, the latter of whom she actually costarred with in his own V-Cinema.
Yasuyuki Maekawa, the actor for Sōichi Isurugi, stated in a press conference that Skyrider and Stronger were his favorite Rider series growing up.
Shogo Muto, the show’s head writer, said in an interview that he became a fan of the Heisei Riders while watching the shows with his son, and that his overall goal with Build is to create a series that kids and adults alike can enjoy.
Prop Recycling: As revealed by merchandise scans, Build's Legend Rider forms are literally just the original Rider costume with the Build Driver in place of their own belt, just like Kamen Rider Decade (ironically enough, he even has a Decade Form). This is presumably a cost-cutting measure, considering several recent Rider shows had specially-made Legend Rider suits that were only used once and then never againnote Though Ex-Aid made the most of it by recycling those suits into ones actually used in the show, like Big Bad Cronus being recycled from Genm Wizard Gamer.
Done in the show with the Smash monsters as its first used as regular Smash and then the (supposedly) upgraded Smash Hazard.
The CGI models for the "energy cobras" that Blood Stalk can summon are actually Venosnaker, Kamen Rider Ouja's Bond Creature; the only difference is that they're rendered in light blue and lack the gold blade-fins along the body.
As with many Rider shows, several later costumes are made by recycling existing costumes, mix-and-matching and repainting parts to make them look more unique.
The Hard Guardian's lower torso is retooled from the Smash.
Grease Blizzard is a combination of Grease's helmet, chest armor and right bracer with the base suit and Destruction One claw arm from Build PhoenixRobo Form, all repainted blue.
Prime Rogue from the Hyper Battle DVD is Rogue's armor (helmet, chestplate, bracers and boots) worn over a spare Build bodysuit, all given tons of gold filigree.
Kamen Rider Blood uses many parts taken from different rider suits:
The helmet is a Build Hazard helmet with the eyes appearing to be Cross-Z’s eyes and Blood Stalks visor.
Evol’s chest armor with a mixture of Blood Stalks.
A Build undersuit with the same arm and leg pieces being colored.
He uses the Great Cross-Z Dragon adapter, inserts the Cobra Lost Bottle, and uses the Hazard Trigger.
In NEW WORLD: Kamen Rider Cross-Z Ryuga gains access to Cross-Z Evol, which is a combination of Evol Black Hole form's horns mixed with Cross-Z's helmet and Evol Black Hole's waist cape. All repainted in Neon and dark cyan. The Muscle Galaxy bottle is a repaint of the Genius bottle.
Kamen Rider Killbus is a repainted combination of made parts of Blood Stalk and Night Rogue/Mad Rogue's helmet, Blood Stalk's shoulders and gauntlets and Hazard Form's feet and shins. The Killbuspider is a remold adapter of the Cross-Z Dragon.
NEW WORLD: Kamen Rider Grease shows Kamen Rider Grease Perfect Kingdom, Grease’s second final form, which is a combination of Grease’s helmet with new add-ons to the helmet, chest armor and lower arm guards, Build bicep and leg armor, and Build undersuit, buts adds a winged jet pack on the back, red castle-shaped shoulder cannons, and blue stag beetle swords on the arms, all colored to represent the Hokuto Three Crows trio. He also uses the Grease Perfect Kingsom adapter, remolded from the Cross-Z Dragon.
Kamen Rider Metal Build, the main antagonist of NEW WORLD: Kamen Rider Grease, reuses the Build Hazard suit, but uses two black tank eyes. His upgraded form, Phantom Build, takes the armor of the Phantom Crushers, and gains more power.
Atsuhiro Inukai's popularity rose significantly after the show ended, with the actor booking quite a few TV shows and movies under his belt and becoming a pretty popular actor in the process.
Eiji Akaso is by far one of the most popular actors from the show's lineup to date, with popularity skyrocketing and his repertoire growing by a significant margin when the show ended.
The Scorpion and Gold Fullbottles were supposed to be among Hokuto's tally of Fullbottles, but they were replaced by Rose and Helicopter.
Similarly, F1 and Kyoryu (Dinosaur) Fullbottles were most likely replaced with Santa and Cake Fullbottles, with fans guessing that there's an issue with the use of the "F1" name. Christmas-themed gimmick items usually are not part of the story (such as with the Santa Claus Eyecon from Kamen Rider Ghost toyline series, or the Holy Christmas Shift Car from Kamen Rider Drive toyline series), but the Santa and Cake Fullbottles are part of the story, likely due to Toei using them as replacement.
Notably, due to the existence of regular Bat and Engine Fullbottles, Toei could have replaced F1 and Kyoryu with regular Crocodile and Remote Control Fullbottles, allowing them to keep Santa and Cake Fullbottles out of the series. It is not known why Toei didn't choose to do so.
It is possible that at one point, a crossover between Build and Kaitou Sentai Lupinranger VS Keisatsu Sentai Patranger was planned, as indicated by a Super Sentai Full Bottle toy (which explicitly shows the 2 Red Rangers from the series, as opposed to a generic Sentai teamnote granted, there's also a Kamen Rider fullbottle which shows Build, Cross-Z, Grease, and Rogue), and a sound effect exists specifically for Build on the VS Changer in addition to the general "Kamen Rider" sound effect, but was scrapped; possibly due to the decision to stop making spring crossover movies (which all previous crossovers had promoted). It is unknown if they cancelled it because of the decision to stop making spring crossover movies, or if they were going to go ahead with it regardless, but backed out at the last minute.
According to rumor they were going ahead with it but realized the plots of both shows wouldn't lend itself well to a crossover, because of Build's unique world circumstances paired with Lupat's conflicting teams (this was before they started cooperating occasionally so Build would have to pick a side to befriend one of them) and scrapped the idea.
Hacking the Evol-Driver reveals 3 additional unreleased Evolbottles - Tank, Lock, and Dinosaur. Tank and Lock were presumably scrapped on the grounds that, with the exception of the Rider Evolbottle, all of the Evolbottles Evol creates have corresponding Organic Fullbottles (and Tank and Lock are inorganic Fullbottles), and Dinosaur was likely scrapped because the corresponding Full Bottle was scrapped as well.
Pin combinations exist in the DX Build Driver for "Cup Noodle" and "Protein Drink" Fullbottles, indicating that Ryuga calling the two food items a Best Match was meant to be the setup for a Brick Joke at some point either in the show or toyline. It was most likely tossed for clashing with the biotic/abiotic setup of the Best Matches.
After Build New World: Kamen Rider Grease was released, Gentoku's actor Kensei Mikami said that he wanted to do a "Rogue vs. Mad Rogue" movie as well, but Grease was billed as the "final chapter" of the Build story so it seems as if that isn't going to happen.
This is Yukari Taki's third appearance in the Kamen Rider franchise, as she previously played unrelated characters in one of the Kamen Rider Double movies and #3 of Kamen Rider Ghost, respectively.
Eiji Akaso (Ryuga Banjo) previously portrayed Hiroki Nagase in Season 2 of Kamen Rider Amazons.
Also making his third appearance is Kouhei Takeda (Kazumi Satawari), who previously appeared as Otoya Kurenai in both Kamen Rider Kiva and Kamen Rider Decade.
Akira Hamada (Juzaburo Namba) previously portrayed Director Tamura, a minor character in Kamen Rider OOO, though he actually made his first appearance in a Kamen Rider series all the way back in Kamen Rider Stronger as Titan.
Ryoko Gi played Yoshiko Tajimi, years after playing the Suzuko Arima/Zone Dopant in Kamen Rider Double.
Assorted Trivia
With the Super Hero Time block being moved, this will be the first series since the revival to not start at 8:00 after its sister Super Sentai series, instead airing at 9:00 before its Sentai sister series.
This is also the last series to have a fully televised run during the Heisei period, due to Emperor Akihito intending to abdicate the throne to his son, Prince Naruhito, thus beginning a new era in Japan effective from April 2019. The last series to air at the end of an era in Japan was Kamen Rider BLACK RX, although in that case, it finished its airing after the changing in erasnote since unlike Akihito, Emperor Hirohito died while in office during the airing of Black RX.
Aside from the aforementioned two examples, Build is the first series:
Since OOO not to cross over with its Super Hero Time Partner, either in one of the Super Hero Taisen movies or a TV special, after Fourze established the yearly streak.
Since Double not to have any sort of Spring movie attached to it.
Since the inception of the Spring movie slot with Den-O & Kiva: Climax Deka not to have A. the non-attached Spring movie premiering during its run be a Den-O movie (Amazons got the honor this time) and B. one of its Riders cameo in that movie to compensate (assuming one counts the Cho Den-O Trilogy during Double's run as one movie).
Since Ghost not to have a Super Hero Taisen movie attached to it.
Since Decade to use "Form" for the name of the various rider forms, instead of using a unique term such as States or Combo.
Since the start of the franchise to have its opening performed by a non-Native Japanese singer.
Since Gaim not to have the succeeding Rider make an Early-Bird Cameo in person in the show's final TV episodes. Instead, a reverse scenario occurs where Sento and Ryuga appear in their succeeding Rider's first two episodes to immediately establish that series as a Crisis Crossover.
Like the immediate preceding season Kamen Rider Ex-Aid and Yuya Takahashi, every episode of Kamen Rider Build was scripted by its head writer Shogo Muto alone, with secondary writers only involved in side material. Muto was also the sole writer for every Build movie except Heisei Generations FINAL and Heisei Generations FOREVER. Incidentally, the former was a crossover with the aforementioned Ex-Aid, and was written by Muto & Takahashi collaboratively.
, the real reason Sento looks so tired is because Atsuhiro Inukai would stay up late at night playing Monster Hunter.