Almost every major character in Kamen Rider Zero-One gets passed the Idiot Ball at one point depending on the needs of the plot.
- Gai Amatsu grasps the Idiot Ball pretty firmly in the second arc, when he chooses to stake his buyout of Hiden Intelligence on a Workplace Competition between his company's Google Glass-esque "ZAIA Specs" and Hiden's Humagears. Apparently Gai didn't realize that, had finished the buyout, he would have had ownership of the Humagears and could have done the competition completely on his own terms, instead of creating a needless risk for Aruto to avert his plans.
- Gai Amatsu also decides to use the Workplace Competition as grounds to test the Raiders, even though he's trying to keep the RaidRiser a secret. Not only that, he uses a brainwashed member of MetsubouJinrai.net to pass the RaidRisers out, implicating him with a known terrorist organization.
- Probably his dumbest mistake of all was creating the Metal Cluster Hopper key and forcing it on Aruto. While it initially made sense since it locked him into a form he couldn't control, he's able to regain control AND use Metal Cluster himself which ended the power gap between him and Gai and lead to him using the form to constantly thwart him for the next dozen episodes. Even if the theory was sound, one would think Gai would lock him into a form that was average at best if not totally weak and not a heavily armored nanomachine controlling super form that was better than everything else at the time so even if he unlocked the Driver it wouldn't help him.
- Gai's lackey, Daiki Kyogoku, grabs the ball briefly when he decides to help his boss win the fourth round of the Workplace Competition. His plan? Steal a RaidRiser and the Scouting Panda key and use them to kill Hiden's representative during the competition. Not only does he accendently set fire to the building being used for the mock fire rescue, it ends up not helping ZAIA's side at all by leading Fuwa to uncover evidence of his cheating and ZAIA's involvement with the Raiders, and it gives the Humagear representative, 119nosuke, a chance to clench the competition for Hiden by giving his life to pave a way for the hostages to come out.
- Luckily for Daiki and Gai, Fuwa himself takes the Idiot Ball right after when he dangles Daiki's ZAIA Spec in from of Gai's face and states how he now has evidence of ZAIA's wrongdoing. This gives Gai a chance to swipe the spec, and since Fuwa neglected to make a backup of the data, Gai is able to cover up all traces of his and Daiki's crimes by destroying it.
- Aruto also grabs the Idiot Ball by just watching Fuwa and Gai fight rather than transforming to help Fuwa, even though he's just as invested in exposing Gai's crimes as Fuwa was, has a lot more at stake with the competition if Gai wins, and had the only Progrise Key stronger than Gai at the time.
- Jin and Yua both take hold of the Idiot Ball pretty firmly later on with their plan to destroy the Ark. You'd think since the Ark is an AI residing in an unguarded sunken satellite near Daybreak Town, the easiest and most risk-free option would be to track down the satellite and destroy it, or even contact Aruto who has possession of Biting Shark. Instead, Jin and Yua go along with the Ark's plan to give itself a physical body, so they can fight it and destroy it once it becomes Ark-Zero. Ignoring the fact that how strong Ark-Zero would be apparently never occurred to them, even if they had destroyed Ark-Zero the Ark still would have been able to revive so long as its satellite body (or whatever it was using as a host) was intact, meaning their plan would have failed no matter what they had done. And because of their actions, the entire "Ark-Zero" arc kicks off.
- Even after they defeat Ark-Zero and destroy Zea's satellite to keep the Ark from possessing it, no one thinks to do anything about the Ark satellite in Daybreak Town. Because of this, the Ark is never actually destroyed and is able continue influencing things, even in spite of As's death. Even post-series it's still at large, where it Wins by Doing Absolutely Nothing as most of the other Riders are either killed or de powered in the MetsubouJinrai incident.
- The Ark itself grasps the ball later on, made worse by the fact that it's supposed to be a super intelligent AI. Firstly, it doesn't remove the free wills of its four followers in MetsubouJinrai.net, even though that would be the best way to ensure they stayed loyal and there no reason why the Ark would have any compunction against doing that, having already done it to them once in the past. Then, after Aruto becomes Zero-Two and defeats it, the Ark arbitrarily comes to the conclusion that Humagears are responsible for its loss and that they all need to be destroyed. It then proceeds to proclaim this to its loyal Humagear follower Horobi, who naturally decides to team up with Aruto to destroy it. This is all in spite of the fact that the Ark is shown to be able to perfectly predict someone's movements and thought process based on their personality, so it should have anticipated how Horobi would react.
- When the Ark is defeated for a third time it tries to reset all Humagears to be loyal to it, which raises the question of why it didn't try to do this immediately after possessing Zea. Had it done this at all sooner, it likely wouldn't have been killed nonchalantly by Raiden firing Breaking Mammoth at it.
- Aruto then takes hold of the ball midway through the Ark-Zero arc when Izu is murdered by Horobi. Not long after her death, Aruto is approached by a long-haired version of Izu who offers him an Ark-Driver to use to get revenge on Horobi. Having seen Izu die in front of him, you'd think Aruto would be suspicious of this doppelganger of her that's appeared in front of him. And considering he'd bore witness to the destructive power of the Ark, even if it was the real Izu offering him an Ark-Driver you'd think Aruto would turn it down. Yet he accepts the Ark-Driver anyway to use to get revenge on Horobi, despite his Zero-Two Driver already being much more powerful than Horobi at that point. Even in the next episode when Aruto clearly becomes aware that she isn't the real Izu and is just using him, Aruto still keeps using the Ark-Driver for some reason, leading to Jin dying needlessly and a Robot War almost breaking out.
- Izu also grabs the ball right before this in quite a stupid way as well. She experiences a vision of Horobi becoming Ark-One and brutalizing Aruto, and doesn't tell Aruto about it even though he's just as invested in turning Horobi good as she is. Instead she attempts to confront Horobi on her own, even though she acknowledges in her conversation with him that Aruto could convince him to turn good. When fighting breaks out, she goes to confront Horobi on her own without Aruto or any other Rider to back her up, leading her to die needlessly.
- Azu, the Izu doppelganger mentioned above, also gets passed the Idiot Ball as well not long after. Considering her plan is to create more Arks, and she's shown to have a stockpile of Ark-Drivers in a vision, you'd think her plan would be relatively straightforward. Just find someone who's sufficiently angry, give them an Ark-Driver and watch them become another Ark. She starts by giving both Aruto and Horobi drivers to turn them into Arks, leading to a Humagear protest breaking out that clashes with police. You would think Azu would take advantage of the protests to pass out more Ark-Drivers and create more Arks, but she doesn't do anything at all, which leads to her plans going kaput as soon as Aruto and Horobi sort things out. The next two people she tries to force Drivers on aren't exactly ideal candidates either. S was motivated by benevolent intentions instead of malice, and Lyon Arkland saw malice as a fickle thing and rejected her advances.
- Fuwa takes hold of the Idiot Ball one last time when he goes to confront Aruto right before his showdown with Horobi. Considering Fuwa had lost his ability to transform and that Aruto very likely wasn't aware of the Humagear protests that were going on and the Robot War that was imminent, the most immediate and rational option for Fuwa would be to explain the current state of things to Aruto and try talking him down from being Ark-Zero. Instead, Fuwa just tells him not to fight Horobi and gives vague reasons why, not empathizing with him over Izu's death at all, and when that (unsurprisingly) doesn't work tries attacking Aruto, even though Aruto far outclassed him on the power scale at that point. Even if Aruto had taken Fuwa's advice and backed down, Horobi by that point was a genocidal terrorist plotting a Final Solution for all of humanity and had become an incarnation of the Ark. Aruto was the only Rider left who could have taken him down, so telling Aruto not to fight Horobi instead of just telling him to put down the Ark-Driver would have left an active threat at large.
- No one tries to make Gai face proper justice for his crimes post-"redemption". Especially if most characters like Yaiba or even Aruto still clearly resent Gai for his past misdeeds. By this point Gai has lost his position as CEO of ZAIA Japan and the influence that comes with it, and he's not an especially strong fighter, so there's no real pragmatic reason to let him stay free, and it's been shown there's ample evidence of his wrongdoing. Despite this, the most Yaiba does to hold Gai accountable is shoot him a disapproving look once in a while.
- Zero-One Others: The duology is heavily reliant on its characters forgetting they're in a technological setting. Metsubojinrai makes no attempt to coordinate with any of their newfound allies (or even back-up their own data and/or bodies, which seems like a weird thing not to do for a group of robots that've upgraded themselves before) despite them having nearly been subsumed by the Mass Brain Key's Hive Mind once already rescuing Jin. After the four link themselves to the same hive the villain wanted them to a second time (preceding this with an ominous announcement that doesn't bother re-assuring people) and getting absorbed into what's now a hostile Mechanical Abomination, Fuwa and Yaiba then spend the second film mindlessly throwing themselves at said abomination instead of sabotaging it in any other way. (Like you'd expect a technologically-inclined police force led by a woman that's dabbled in data-transfer the whole show to attempt) Fuwa then writes the Metsu foursome off as dead/wanting to die (despite a clear indicator they're Fighting from the Inside that saves Yaiba's life when she actually tries attacking the Rider's Driver) based on a vague conversation he had with Horobi once and is given the tool to kill them by the firmly pro-Humagear Hiden Intelligence, (the company that can produce Humagear bodies whenever they want) which he uses to Mercy Kill the berserk Rider at great cost. The events of the V-Cinemas only end as tragically as they do because the heroes of both films forget they have arsenals and only half-heartedly coordinate, railroading them into making Senseless Sacrifices.
