Artificial Stupidity: As in other Musou-type games, mooks seem to share only one brain among all of them, and end up just standing aroung you not doing much, or at least not doing anything fast enough to prevent you from getting combos in the hundreds by hitting them repeatedly and in packs of twelve.
Big Bad: Karas, an evil sprite/fairy/whatever of the same species of the one that guides the Riders.
Call Back: Using certain Riders to unlock others (via the "(Rider)'s Awakening" stage) will yield special dialog; for example, using Double in Fourze's Awakening will have Shotaro recognize Gentaro as "that pompadour kid", which is what Shotaro called him in Movie Wars Megamax
Cool Bike: All characters can summon their bike (except Accel, who becomes a bike, and Beast who just uses his Falco Mantle to fly) during stages to get around faster. Their primary purpose is to let you travel between fields quickly, but aren't amazingly useful for that due to clunky controls, and have basically no combat use whatsoever (since you can't fight on your bike and enemies will roll out of the way).
Demoted to Extra: The Second Riders who are non-playable, including G3-X, Knight, Kaixa, Garren, Ibuki, Gatack, Zeronos, Ixa, and Diend. Made even more surprising when you consider that the advertising made a big deal out of their getting several Rider actors to reprise their roles...only for them to be NPCs (this list includes Garren, Gatack, and Diend). Future DLC might avert this, but so far nothing has been said.
Also arguably the Joker Undead, who is not only voiced by his original actor Ryoji Morimoto, but never changes into Kamen Rider Chalice.
It is justified with Diend, since he is one of the few Riders not to have a motorcycle, which are somewhat important for the gameplay.
Downloadable Content: Will get free DLC with new Rider Forms, mainly Wizard Infinity Style and Beast Hyper. Showa Riders are also rumored.
Kamen Rider Mage Mayu Inamori from Wizard has also been rumored.
Exposition Fairy: A Navi-like golden fairy by the name of Canary joins Wizard and helps him find the other Riders and go in their memories to remind them that they're supposed to be heroes.
Final Boss: Karas himself in Decade Violent Emotion form, helped by Eternal, Skull and New Den-O.
Finishing Move: Strangely, killing bosses requires you to hit them with your characters Triangle+Circle move, even if for some, it's not their usual finishing move or even a particularly powerful attack. Den-O's Hissatsu Part 2 or OOO's Tatoba Rider Kick are fine, but Beast only being able to finish bosses off with his Buffa Mantle; Or Fourze Cosmic States using his Rocket and Elec combo when he uses his Super Galaxy Cut upon transforming seems weird...
This occurs mainly with Super Modes because the game often has the Rider's most iconic finishing move (like the Super Galactic Finish) as the attack that occurs when you change into your Super Mode, meaning you can't use it normally. There are a few exceptions; Decade Complete's Final Attack Rides can be used any time by pressing R2, but cost about half your Super gauge.
Get Back Here Boss: Some of the bosses flee from you and restore your health 100%, it's annoying at times. The worst is Douji.
Lampshade Hanging: If you use Decade to awaken Kuuga, Tsukasa will have special dialog where he recognizes that Godai isn't the same Kuuga he traveled with, but says that they both had the same desire to protect peoples' smiles.
Laser-Guided Amnesia: Most of the Riders seem to have forgotten who they were, and have to be reminded of their roles as heroes by Wizard. The opening stage, "Rider War?", sees Wizard appearing in the infamous BBC Quarry and getting attacked by the ten Heisei Riders, lead by Decade.
The levels in the game, at least for a good half of it, are based off events that occurred in the show, nearly all of them set during the end game of their respective show save for Hibiki (for reasons unknown) and Wizard (his show was airing at the time, and thus there was no endgame yet).
Faiz's Blaster Crimson Smash leaves a huge shockwave at the kick like what happened in The Movie. Though Fridge Logic kicks in when you realize that the reason why it left a shockwave was because Faiz was Rider Kicking a photon charged BFS.
Original Generation: The Kamen Rider Eternal who appears in this game is an entirely new character, as opposed to Katsumi Daido or Jun Kazu.
Personal Space Invader: The Waste Yummies can grab you. And that's it. They just grab you from behind and prevent you from moving for a few seconds.
Point of No Return: When you battle another Rider you can't escape the area you're fighting in, either a door or an invisible wall stops you.
Humorously, one of Kabuto's lines is "if you value your life, you best turn around and leave". But you can't. Irony.
Power-Up Letdown: Kiva and OOO's alternate forms only have a single special attack each; OOO partially makes up for this by having some of his Combos' powers pop up in his regular melee combos (for example, Gatakiriba's combo ends with him blasting the surrounding area with electricity).
Theme Naming: The small faeries that follow the heroes are named after kinds of birds while the domain they live in is the "Bird's Cage."
Super Mode: As most characters' Limit Break by pressing R2 when their gauge is full. They first use a powerful attack, most often their Super Mode's Finishing Move, and can then fight for some time with their new form's increased power and new moves until the gauge is completely empty.
Suspiciously Similar Substitute: Even though the Kuuga in this game is confirmed to be Godai, Onodera makes a kind-of appearance as one of the Riders you fight in Decade's Awakening.