- Ascended Fanon: Joriri was originally one of the fan designs submitted to the Keroro Land mangazine, before being incorporated into the TV show.
- Cancellation: The series was originally going to be dubbed and shopped to children networks by ADV Films before they went out of business. Funimation dubbed the first 78 episodes, but ceased production due to being unable to secure a TV broadcasting license on a major children's network, probably because the series was still too risqué by American standards (even though things like Koyuki's blatant crush on Natsumi had been toned down in the first place, though networks probably thought people would pick up on the subtext anyway, and didn't want a repeat of the "Sailor Uranus/Neptune are cousins" debacle).
- Cross-Dressing Voices: To be expected in any anime with pubescent boys — keep that in mind when you listen to Keroro, a veteran soldier and avatar of the very otaku who watch this show. There's a reason all his female impersonations are so realistic.
- Keroro averts this in the Funimation dub. Of course, in both versions, Tamama and Fuyuki are voiced by women.
- Development Gag: In episode 12-B of the English dub, Kululu accidentally calls Giroro "Giro" — which was his name in the preliminary dub (of that same episode no less).
- God-Created Canon Foreigner: Katoyama Kiko, a human mecha designer who joined the Keron Army for a while, and also Mois' friends, girls with similar missions to judge and destroy planets, like Maya, Luz and New, who appear in one story of the last season of the original anime, were all created by Mine Yoshizaki but have made no appearances in the manga at all, not even in small cameos.
- Late Export for You: Only the first 78 episodes were dubbed by Funimation. Further, those were the only episodes released in North America until Discotek announced they would release all 358 episodes to Blu-ray.
- No Export for You: The majority of merchandise and games based on the series, as well as the anime for a long time. Though maybe the former will change now that the latter has.
- The Other Darrin:
- In the Japanese, Fuyuki was originally played by Tomoko Kawakami. However, she left the show about two-thirds of the way through its run and was replaced by her longtime colleague Houko Kuwashima (who incidentally took over several of Kawakami's other roles later after Kawakami died of cancer in 2011).
- Jirara, the leader of Dororo's former assassin unit, had a completely different voice actors and style of voices in the 7th season flashbacks compared to the 4th season story which featured him. In the 4th season, he sounded like a cold warrior type, while in the 7th season, he sounded like an old mentor.
- This is also the case for minor character Melody Honey, in her initial appearance in Seven of Seven, Melody Honey was voiced by Naoko Matsui, however in Arcade Gamer Fubuki as well as her appearances in this series, she's voiced by Megumi Toyoguchi.
- In a dub example of this, for Saburo's first animated appearance in Seven of Seven, he was voiced by Sebastian Arcelus note , but in this series, Joel McDonald voices him, granted this is justified since not only is Sebastian a New York based actor note , he had also moved on to doing live action and stage work by this point so hiring him would've been way above Funimation's pay grade.
- The Other Marty: Keroro, Kululu, Natsumi, and Mr Narrator were recast between Funimation's preliminary tryout dub of episode 12-B and their released dub (Giroro and Tamama remained the same). It seems like they didn't even re-record Brina Palencia (Tamama)'s lines. For the record, in the tryout episode Chris Cason was playing Keroro and Todd Haberkorn was playing Kululu.
- Playing Against Type: Junko Noda, seiyuu of Karara, doesn't usually voice Genki Girl's often.
- Quote Source: TakeThat.Anime
- Referenced by...:
- Keroro and Tamama's heads appear in an episode of Lucky Star.
- Sgt Frog has had a few Abridged series and one-shots, the best known being Sgt. Frog Abridged by TheMidnightFrogs.
- A HK TV Drama has referenced the manga via the names of the characters. (page is in Chinese)
- Talking to Himself:
- Keroro meets an alien version of his own seiyuu, Kumiko Watanabe. Sadly all her future appearances are scarce on dialogue.
- Dororo and Dokuku share the same seiyuu.
- Keiji Fujiwara as both the Narrator and Paul may be old news now, but one recent episode plays this trope to the letter when Paul explains an important plot point to the Narrator. This is not the case in the English dub, where Kent Williams plays Paul and R Bruce Elliot plays the Narrator.
- In the dub Leah Clark plays both Fuyuki and Lavie (who, admittedly, don't really share a lot of scenes) and Todd Haberkorn is Keroro and Dance*Man
- Dororo-mama shares a voice actor with Keroro.
- What Could Have Been: A large example from the English version due to its Development Hell. Keroro was originally going to be voiced by Vic Mignogna when ADV had the series (and Jessica Boone was to voice Natsumi). However, when Funimation picked up the show, everyone was recast. Keroro was played by Chris Cason in the test dub of Episode 12B, but was changed again in the final release to Todd Haberkorn, who in the test dub voiced Kululu, whose voice actor changed to Chuck Huber. Chris Cason still does make an appearance in the dub as Taruru, however. In fact, the only voices from the test dub that weren't changed for the final cut were Giroro and Tamama (Christopher Sabat and Brina Palencia respectively). Hell, even most of their lines were unchanged from the test dub.
- The dub was also going to have some name changes, such as changing Natsumi to Natalienote and removing the third syllable of the frogs' names (Keroro became Kero, Tamama became Tama, etc). This was changed due to negative reception, and they instead went with the original names for the characters.
- Had the English distribution rights remained to ADV, the show would've aired on television in the United States. Cartoon Network liked a mass-media pilot and Nickelodeon liked a kids' pilot (in fact, Nick said they would air the show if ADV got merchandising rights). To this date, the Funimation dub has never aired on television in the United States outside of their own channel, and no network has picked it up.
- The Wiki Rule: Keroro Wiki.
aka: Keroro Gunsou