With the exception of the non-canon Dark Decadenote Who would have been canon, had The Last Story not been Screwed by the Network, all riders with "Dark" in their name have appeared in some form of media involving Ex-Aid - Dark Kiva appears in the Beast Rider Squad special, and Dark Ghost, Dark Kabuto, and Dark Drive all appear in Kamen Rider × Super Sentai: Chou Super Hero Taisen. However, with the exception of the aforementioned Dark Drive and Dark Ghost, none of the dark Ridersnote as in the villains from the summer movies for Kamen Rider series - i.e., Eternal, Orga, aside from Ex-Aid's Fuuma, have appeared in media involving Ex-Aid.
Every single episode of Kamen Rider Ex-Aid and nearly all of its movies were penned by head writer Yuya Takahashi alone with no additional writers helping him, though some did write a few specials that he supervised. Previously, the only made-for-TV Kamen Rider season to have been written entirely by its head writer without others was Kamen Rider 555 (not counting the Amazon Prime series Kamen Rider Amazons, which also has every episode written by the head writernote Ironically, the only installment she didn't write, the Grand Finale movie, is instead written by Yuya Takahashi under her supervision).
Inverted with Ren Amagasaki/Lovelica Bugster. Shinya Kote plays Ren in his human form, while Jun'ichi Suwabe voices him in his Bugster form. Suwabe's voice is dubbed over Kote's performance when Ren is using his Bugster abilities in human form.
Also played with with Emu and Parado. Hiroki Iijima plays a Parado-possessed Emu, and Shouma Kai voices (temporarily) Ex-Aid Level XX R.
The Cast Show Off: Hiroyuki Takami who plays Masamune Dan/Kamen Rider Cronus, is also the singer for the legendary Japanese band, ACCESS. In the series, he sings WISH IN THE DARK, showing off his vocal chops. Later, he also sings JUSTICE, his own character's image song.
Colbert Bump: "Time of Victory" received a bump in popularity after Dingo Doodles shouted it out as a possible theme for Erina.
This Anime News Network article about the debut of Poppy as a Kamen Rider initially called her the first female Kamen Rider even though there's been multiple female riders a fewtimesbefore. Fortunately, they corrected the article not too long after posting it to clarify that Poppy is the first female rider with her own exclusive transformation device. At least until Cronus debuts, since he uses the same device. Even then, she doesn't count as such, because Natsumi Hikari is the first female Rider with a unique device and with Cronus' debut, still holds that unique distinction. Yes, she relies on a Kivat like Kiva and his variants, but unlike the latter ones, she doesn't use a belt, just the little bat herself as a trinket, not unlike a Magical Girl's trinket. Although if one was to exclude movie-exclusive riders, which Natsumi falls in the category of, then Poppy would have held that distinction until the debut of Chronus. However, Poppy does have the distinction of being the first lead heroine to become a Rider in a main series, something which would become much more common for the franchise moving forward.
A mistranslated news of Ex-Aid being featured in an anime magazine sparked a minor uproar amongst fans and misinformed articles over the possibility of the series getting an anime adaptation/sequel. In actuality, the article was a feature in regards to the use of CG animation in the final battle of True Ending, and was never an anime adaptation announcement at all.
Dawson Casting: Inverted. As revealed in the Ex-Aid character book, Taiga is 29 years old, making him the oldest of the four main heroic riders in Ex-Aid. However, in an inverse of this trope, his actor was 22 years old at the time of the show (he was born in 1994). It's the same with the other actors. Kiriya is 27 years old, while the actor playing him was 23 years old (1993). Emu and Hiiro, who are both 24, are played by actors who were 20 (1996) and 21 (1995) at the time, respectively. There are also aversions with Kuroto and Nico, whose age are the same as their actor/actress (1986 and 1998), which are 30 years old and 18 years old, respectively.
Mighty Action X was released as a legitimate 3DS game to promote this series. It can be downloaded through a code after purchasing All Kamen Rider: Rider Revolution, provided you have a Japanese Nintendo eShop account (and a Japanese 3DS to boot).
As 2017 is the fifteenth anniversary of Kamen Rider Ryuki, Takeshi Asakura/Kamen Rider Ouja returned in a special starring Hiiro/Brave, portrayed by his original actor. Furthermore, in Chou Super Hero Taisen, Shuichi Kitaoka/Kamen Rider Zolda returned as one of the main protagonists alongside later heroes. Not to mention Parado's Level 99 transformation pose is similar to Ryuki's pose when he's about to execute his Final Vent.
Similarly, it's the tenth anniversary of Kamen Rider Den-O, hence why the Imagin gang are back in the Chou Super Hero Taisen movie.
One-Steve Limit: Averted in a meta-sense, both of the actors playing Parado and Graphite have the same first name, Shouma.
Hiroki Iijima/Emu Hojo and Toshiki Seto/Hiiro Kagami are fans of Kamen Rider Ryuki, to the point that their favorite Riders are Shinji Kido/Ryuki and Takeshi Asakura/Ouja respectively. Seto would even costar with Asakura in Kamen Rider Brave: ~Let’s Survive! The Revived Beast Rider Squad~.
Shouma Kai/Parado is a massive fanboy for Kamen Rider Kuuga, which he made abundantly clear in most of his answers during a post-Ex-Aid cast interview.
The initial rusted form of Brave’s Gashacon Sword as seen in #2, upon closer inspection, is clearly a painted Kuuga'sTitan Sword, only with the guard horns facing down.
The Ghost, Drive and Gaim Gamers suits are recolored Ex-Aid Level 2 with different helmets and armor.
The Bandai Namco forms are recolored of the Level 3 armors
Pac Gamer: recolor of Robot Gamer with new gloves.
Famista Gamer: recolor of Best Gamer with the turntable removed and adds a glove.
Xevious Gamer: recolor of Combat Gamer with remolded chest armor.
Ex-Aid’s Bike Level 0 form is Lazer’s chest armor and wheels, and giving Ex-Aid yellow hair.
Ex-Aid’s Knockout Gamer Level 39 form reuses the Pac Gamer chest, head gear and gloves, but uses the Level 2 shoulder pads.
Brave’s Night of Safari form is the Hunter Gamer repainted in the colors of a leopard, with the head of a Lion.
Lazer’s Level 0 form reuses the same suit of Ex-Aid, but with his head.
Lazer Level X recolored his Chambara Gamer suit to turquoise.
Genm Level 0 looks like a Ride Player suit with Genm’s armor.
God Maximum gamer is Ex-Aid’s Maximum Gamer in the color of Genm.
The Ride Players' weapons are repainted versions of the weapons used by the Mooks in Kamen Rider Ghost, which were in turn repainted versions of the weapons of the Riotroopers in Kamen Rider 555.
Kamen Rider Cronus' costume seems to be built mostly off of Genm's Wizard Gamer form (most obviously the Badass Longcoat) with elements of the Ride Player costume. The helmet also appears to be based off Genm’s helmet with the crown looking like the concept art from Genm Shakariki Spirts.
The Ninja Players in the movie is essentially Fuma’s suit with the fins off and a helmet with one eye.
During the Kamen Rider Genms - Smart Brain and the 1000% Crisis- special, Kuroto gains anew form by absorbing Ark’s malice to create a new power up, Genm Musou. The suit is his Level 0 suit, with a new helmet in the similar shape of Ex-Aid Muteki Gamer, with dreadlocks in the back, but with some kanji sticking out, new shoulders with kanji, and lower arm and shin armor and feet. The Genm Musou Gashat uses the same mold of the Gashat Gear Duals, but with a new knob on the front.
Recycled Script: Not exactly same, just similar. Kamen Rider OOO there was an episode with a genius surgeon held back by her father, the director of the hospital she worked at. She was banned from performing operations on anyone and was justifiably angry, which made her a perfect piece in Kazari's next plan. The reason was that her father didn't want her to become surgeon with all the skills, but no compassion and responsibility as he put it. Enter Hiiro, another genius surgeon, who treats patients as procedures and has little respect for anyone, who does otherwise. Also, he avoids taking responsibility for risky operations. In his case, it's Taiga, who brings this up. Ironically enough, Hiiro's father indeed is a hospital director, but too much of a absent minded weirdo to thought anything like this.
The office of Kyotaro Hinata, the Minister of Health, is the same room as Soichi Makage’s office in Drive and the main office of BOARD. And if you look closely enough, even some props made a comeback!
When Seiji Takaiwa was filming his scenes in the Ex-Aid Level 2 suit, he ad-libbed the “blowing into your cartridge trick” thing before performing the Rider Kick. That being said, the film crew were actually damn cool with it and allowed him to continue doing it indefinitely.
As detailed on the Funny page, Kuroto’s characterization as an Evil Is Hammy maniac with a god complex is the result of his actor ad-libbing a particularly crazed Evil Laugh in one scene and them rolling with it.
Trolling Creator: Toei seems to enjoy trolling Kiriya fans after his death, ranging from releasing a t-shirt depicting his death and causing a massive uproar on Twitter.
In the original script, Emu is supposed to have a big sister who plays games with him and wants to become an idol despite her fragile body. The writer didn’t include that big sister because they've noted that she’s a blatant Expy of Karen Hojo from The Idolmaster franchise, which Yuya Takahashi is a fan of. Incidentally, Emu’s surname sounds exactly like as Karen’s, probably as a tribute to her. Since several plot points regarding Emu's backstory rely on him being an only child (especially in regards to unconsciously creating Parado out of loneliness), the series would probably have taken a very different turn if such a sister had existed.
Reportedly, Break The Darkness by Rider Chips was intended to be the insert song for either Maximum Mighty X or the Kamen Rider Chronicle arc. However, it was pushed aside in favor of People Game, and was eventually used for a Pachinko Machine of Kamen Rider BLACK. Interestingly enough, this led to Maximum Mighty X being left without an insert song despite the series having them, much like Agito's Burning form.
The series itself started off in development as being about games, and Emu was originally going to have Parado's personality as "a gamer who doesn't understand the concept of life and death", but once the medical drama aspect was added, Emu's character was reworked into a medical resident and the original concept reused for his "Genius Gamer M" personality and Parado. Mighty Novel X brings it somewhat full circle by revealing that Parado's personality comes directly from Emu's own child self prior to the accident.
While Kuroto's resurrection was always planned, it was originally supposed to have been much later into the story, with him staying dead for almost the entire Kamen Rider Chronicle arc and only coming back for the concluding True Ending arc. It was Takahashi's fondness for the character and Iwanaga's performance that led to him being brought back earlier and entering an Enemy Mine situation with the other Rider's, becoming a core part of the cast in the process.
.