Development Gag: There is a game-exclusive team named Dummy Emperors which includes all the members that became the Dark Emperors in the second game/season, plus Ootani Tsukushi and Tamano Gorou, who were originally planned to be part of the latter team.
Apparently, the reason why the characters have English names in Europe (despite they explicitly say they're Japanese) is because the European publisher of the anime wanted to repeat the (insane) success that Captain Tsubasa got during the early 90s. Guess how were the characters of that series named in Europe.
Averted in the Mexican Spanish dub, albeit Mamoru Endo was renamed with Satoru Endo, since Mamoru sounds like a offensive slang in Spanish.
The Reveal that Ishido Shuuji was actually Gouenji Shuuya. The same seiyuus, the fact that Gouenji's character design for GO wasn't out yet, and even several similar details they have.
Lee Kobun being the same person as Mutekigahara Fujimaru is one for most people during Orion. However, the fact that Fujimaru is actually one of China's representatives and China's very own captain, plus the fact that China's team are also personally coached by Zhao Jin Yun before, caught many by surprise.
Many fans called for Atsuya being chosen as one of the new members of Inazuma Japan in Orion.
No Export for You: Europe already received the anime series, the first 5 games, and the Strikers spin-off. It's been so successful that they are very likely going to release game 6. North America, on the other hand, got the first game and the first season, and is still waiting for everything else.
Seems to be the case with European Galaxy, after news came out that Level-5 was sued for having Galaxy in the name. While the case ends this year, whether Level-5 chooses to release it remains uncertain.
On the last episode of Go's first season a girl with a rainbow theme and a boy with a metalic theme were featured with their own hissatsu. The characters and the hissatsu were the winning submissions of a contest where a fan-character and a fan-hissatsu would be animated in the series.
Then you get Mecha Endou who appeared in Chrono Stone during the match between El Dorado Team 2 against Giru, one of the hissatsus he has (Penguin the Hand) and his Keshin (Eichi no Ou Bunguou) are also based on a fan-submitted content.
Two members from Tonegawa Tousen in Ares no Tenbin, Tanukigahara Ponko and Muhyou Jou, are both fan characters during a competition for Inazuma Walker in 2017.
In the Japanese version, Haruna is voiced by Kakazu Yumi in the first game, while in the other games and in the anime, she is voiced by Sasaki Hinako. The same applies to Shourin if you replace them with Etsuko Kozakura and Masako Jo, respectively.
Hibiki is voiced by Shuuichirou Moriyama in the first game and Kinryuu Arimoto for the rest of the original series, as well as the GO series. In the Ares series, Arimoto is replaced by Tetsuo Kanao, due to him being diagnosed with cancer and retired from dubbing (and as of February 2019, dead).
A crazy example for the Italian dub. In the anime, which was released one year before the games, Gouenji's voice actor is changed somewhere around the beginning af the arc based on the second game's plot. In the first game, Gouenji has the second anime voice... which is replaced in the subsequent chapters with his first anime voice.
One example is that some voice actors worked together in Code Geass among the cast in Ares. Nosaka is an exiled prince starting a rebellion against his former home under the alias, Zero. With a best friend and rival in Mansaku/Mizukamiya, Tatsuya is Nosaka's little brother in a loose sense, and Aki is Nosaka's classmate who is a good friend of his but is left out of the loop about his actions as Zero.
It's bad enough Nintendo put an embargo on Inazuma Eleven's UK release (Never mind the fact it was LOCALISED THERE) such that the game was unavailable in the UK until the anime aired. But Disney XD really didn't give a rats ass about the series, punting it on at 8:30am in the morning (albeit in the summer but still) and then pulling it off air 26 episodes in. If not for how they treated Naruto when they were Jetix, this would be considered one of the most egregious examples of screwing a show over by any UK Television company.
Even more Egregious in Latin America. ZAZ (all Latin America)note the channel died on July 2014., VivaSports (México)note is private and ETC TV (Chile)note and stays there. The series is very popular there too are the only ones consistently airing the series with a decent schedule, also in Brazil where the series is a huge success. But what about other countries's networks in the region? Every one of them screwed the series, airing it at 5:30 A.M in Ecuador and Perú, eventually pulling it off air; inconsistent airings and schedules in CityTV in Colombia, also pulling it off air in favor of a block with only Nickelodeon showsnote but they will never put off air Dragon Ball Z, (however in Peru it even got 'worse' for the 'anime in general').
Junko Takeuchi voices both Endou Mamoru and his great grandson from the future, Endou Kanon, who traveled to past to help his great grandfather. Naturally, they interact a lot in the movie.
Mamoru Miyano voices the Fubuki brothers, Shirou and Atsuya. This overlaps with Talking to Themself when Shirou speaks to the Split Personality of his twin, but in the Ares timeline they get to speak to each other as different individuals, since Atsuya is alive. In fact, in many languages they're voiced by the same person.
Yuuki Kaji plays both Kozoumaru and Fudou. Kozoumaru gets to speak to him in episode 10 of Ares, when he calls him (and Sakuma) out on the fact that Teikoku uses dirty tricks to win the matches.
Megumi Tano plays both Kabeyama and Sakuma. This would be more of a case of "talking at the same time", but they create a technique named Deep Jungle (together with Kazemaru)in the Inazuma Eleven vs Danball Senki movie. They don't interact too much otherwise, despite both being members of Inazuma Japan in season 3, being so far the only main characters voiced by the same person in the Japanese dub.
The English dub of the anime has a few examples.
Richard Magarey voices best friends Kabeyama and Kurimatsu.
Michael Pizzuto voices Hiroto, Midorikawa and Kira Seijirou. Hiroto interacts with both of them, the former due to being his best friend and the latter his adoptive father.
David Lee McKinney voices a lot of characters, including Gouenji and Aphrodi, who get a fair share of interactions during the time Aphrodi joined Raimon in season 2.
Throw It In!: Kurumada's "shupoh!" was an ad-lib the first time.
Gouenji Shuuya's first name was originally Harusuke and one of the original plans was to have the members named after seasons. In the end, only the managers fit into the Temporal Theme Naming.
Kazemaru and Kabeyama were originally supposed to be called with the other's surname, which is ironic to say the least. This is the reason why their names were switched and fit much better.
Tamano Gorou and Ootani Tsukushi were originally planned to be members of the Dark Emperors before they were changed with Sugimori and Nishigaki. There is, however, a game-exclusive team named Dummy Emperors, which includes them.
Hikaru was originally planned for Teikoku instead of Raimon, as the first concept art of him has him wearing the Teikoku uniform.
Okuiri, along with Hattori, were planned to be defenders while Mansaku was planned as a midfielder as shown in early game pictures before Ares' anime release.
In the earliest stages of development, Mansaku's last name was Bansaku, while Michinari Tatsumi's first name was Tatsuya.