- Name's the Same: Mr. Sakurai, the English teacher and Mrs. Sakurai, the head of school, are not related. In the anime, Mr. Sakurai is renamed Sakurada to prevent confusion.
- The Other Darrin: Where do we begin with this one? On the Japanese side, when the GTO anime was created, none of the actors from the original Shonan Junai-gumi OVAs returned to their parts. Granted, there weren't many returning characters from the latter besides Ryuji and Onizuka himself, but still. The only returning actors in GTO were Shin-ichiro Miki, Hisao Egawa, Yasunori Matsumoto, and Yuri Shiratori in completely unrelated parts.
- Wataru Takagi replaced Issei Futamata as Onizuka.
- Isshin Chiba replaced Hideyuki Hori as Ryuji.
- Kazuki Yao replaced Ken Narita as Saejima.
- Kae Araki replaced Megumi Hayashibara as Nagisa for her brief cameo.
- Plus Kaya Matsutani replaced Michiko Neya as Nao Kadena.
- Within Shonan Junai-gumi itself, Takumi Yamazaki voiced Tsuyoshi Tsukai for the first two episodes, but was replaced for some reason by Toshiyuki Morikawa in the fourth. Morikawa also voiced the villain of the fifth and final episode, Kunito Nakajo.
- Also, in the GTO anime, minor supporting teacher Koji Sannomaru was voiced by Tsutomu Tsuji for his first couple of appearances before being replaced for the remainder of the show by Hirohiko Kakegawa.
- On the English side of things, the GTO anime had many inconsistencies with its supporting cast. Most of the children of Class 3-4 were subject to recasting depending on whether some actors were available or not to record. The only students who didn't fall victim to this at some point were Fujiyoshi, Kusano, Tomoko, and Urumi.
- In particular, Kirk Thornton was for whatever reason unavailable to record for volume 4, so his roles were filled in by Doug Erholtz (Yoshikawa) and Dave Wittenberg (Kikuchi, Ryuji, and Sannomaru). Kirk would return for the remainder of the series with volume 5.
- Kunio was first voiced by Bryce Papenbrook in episode 4 (alongside his father who voiced Uchiyamada and some extras) before being replaced by Tony Oliver for the rest of the run. Bryce was attending college at the time and couldn't devote any more time to the series.
- Speaking of the fourth episode, another oddity was that Anko and Miyabi's actresses, Dorothy Elias Fahn and Wendee Lee respectfully, originally had their roles reversed with Wendee even voicing Anko in the preview for the next episode. After this, Dorothy stayed with Anko for the remainder of the show except in volume 3 when she wasn't available, so Cindy Robinson voiced the character for episode 14. Wendee would continue on as Miyabi from episode 7 to the series' end.
- That was nothing compared to their Girl Posses, who never had consistent actresses in the dub. Poor Saeko had a grand total of FIVE different actresses voicing her across all her appearances! First Christine Ruprecht voiced her in episode 7, next Philece Sampler in episode 9, then Debbie Rothstein was settled on as the de facto voice (with Wendee Lee filling in for volume 4). However, Debbie did not return for volume 7 and onwards, so Cindy Robinson finished up for Saeko's remaining speaking parts. Chikako faired far better in comparison; she was mainly voiced by Sampler with the sole exception of episode 16, where Kate Higgins filled in.
- As for Anko's lackeys, Mayuko was voiced by Debbie Rothstein for volume 2 but way down the line in volumes 9 and 10, because of the above mentioned with Saeko, was replaced by Kate Higgins. Naoko, on the other hand, had four different actresses. Cindy Robinson voiced her in volume 2, but since she was now filling in as Anko for that volume, she didn't return as Naoko and was replaced by Christine Ruprecht. Since Cindy was already voicing Saeko for the Okinawa episodes, Naoko was recast a third time with an uncredited Lara Jill Miller on volume 9. Miller did not return for the final volume so Naoko had to be recast yet again, this time with Karen Strassman.
- Two members of the Holy Forest staff also fell victim to this in episode 3, with Brad Rowen and Wendee Lee voicing Sakurada and Kochatani, the latter was especially noticeable since the male teacher was voiced by a woman. Steve Blum, already voicing Onizuka and Fujiyoshi, would take over as Kochatani for the rest of his speaking appearances while Tony Oliver would voice Sakurada in episode 6 only before handing the role to Dave Wittenberg for the rest of the run.
- Saejima was voiced by Richard Epcar (already Fukuroda) for his first two appearances but was replaced by Skip Stellrecht for his remaining three outings.
- Finally, there's Uchiyamada's wife and daughter, Ryoko and Yoshiko. Originally, they were played by Debbie Rothstein (Uchiyamada's English voice's actual wife) and Dorothy Elias-Fahn in volume 1. In the second volume, however, while Dorothy was still Yoshiko, Wendee Lee had taken over as Ryoko. It was strange considering that Debbie was in volume 2 voicing Mayuko and Mrs. Uehara. Later still in volume 6, where the vice-principal got A Day in the Limelight, both Uchiyamada women were recast again with Kate Higgins voicing Yoshiko and Philece Sampler providing Ryoko's voice. It's, again, strange since Dorothy was also in the volume voicing Nao.
- On a minor note, Tomoko's father was voiced by Dave Wittenberg in episode 9 but got replaced by Tony Oliver in the penultimate episode.
- Relationship Voice Actor: One of many things that boasts GTO is having the voices of the main characters of three Gundam series, specifically Garrod Ran as Onizuka, Heero Yuy as Kikuchi, and Domon Kasshu as Murai.
- Romance on the Set: The live-action actors of Onizuka and Fuyutsuki ended up together in Real Life.
- Star-Making Role: Onizuka was Wataru Takagi's breakout role as the main character.
- Unintentional Period Piece: The fact that Ape Escape is used as Product Placement in the anime sets the series during the 90s.
Trivia / Great Teacher Onizuka