Originating as a gag-manga by Mine Yoshizaki, published in Shonen Ace starting in 1999, and every bit as goofy as its English titleSergeant Frog would suggest, Keroro Gunsou is the story of a not-so typical Japanese family and the alien frogs who turned their lives upside-down.When pubescent paranormalist Fuyuki Hinata and his tomboyish older sister Natsumi (13 in the anime, 14 in the manga) discover an alien in his bedroom, it's just the beginning of their troubles. This alien, Sergeant Keroro, is the leader of a recon team for an alien invasion from Keron, "the 58th Planet of the Gamma Nebula". But once his superiors realize he's been found out, they abort the mission and leave him and his crew behind. With no one else to turn to, Keroro ends up staying at the Hinata house with Fuyuki, Natsumi, and their mom Aki, living as something between a servant and a pet.Of course, Keroro is still an invader, and still plotting the downfall of "Pekopon" (his species' name for Earth in the anime — Pokopen in manga)... when he's not doing chores for the Hinata family, or being distracted by such aspects of Earth culture as Gundam model kits and the Internet. Before long, Keroro manages to reunite with his squad-mates: hot-headed rookie/Keroro fanboy Private Tamama,hard-boiled combat specialist Corporal Giroro, and smarmy intelligence officer Sergeant Major Kururu/Kululu. With this eclectic crew (plus some hippy lance jack, Do...uh, rodo?), Keroro attempts to conquer the planet through one convoluted scheme after another, though sometimes he feels torn between his mission and his obligation to the Hinata family... but not that often.Surprisingly, for a series that's not meant to be taken seriously, often has No Fourth Wall, and is frequently brimming with pop-culture references, it has a lot of heart. Though it stops far short of being sappy, there are many heartwarming moments sprinkled in that sometimes constitute Tear Jerker material. It's still firmly in the comedy genre, though, and hence, occasionally brings these scenes to an abrupt halt with a quick joke.Rounding out the cast is an assortment of eccentric humanoids, including Momoka Nishizawa, bi-polar scion of a multi-billion-dollar international corporation who hangs out with Tamama and has a serious crush on Fuyuki; Mutsumi Saburo, a smooth talking poet/artist/radio show host who hangs out with Kululu; Koyuki Azumaya, New Transfer Student and Ninja girl who hangs out with Dororo and is a rather close friend of Natsumi; and Angol Moa/Mois, a ditzy alien girl who has a crush on Keroro and the power to destroy an entire city block with literally a fraction of her power ("Armageddon One Ten-Millionth!").Insanely popular in Japan, the manga was eventually released in North America in 2004 by Tokyopop, with the title Sgt. Frog. An anime adaptation naturally followed, also begun in 2004. In November 2006, ADV Films announced that they had acquired the rights to the anime version. However, after nearly two years without a single word on the project save for a couple of trailers, Funimation acquired the distribution rights in 2008 (along with about 30 other ADV titles). After a bit more Development Hell, the first season 1 DVD was released September 2009. Episodes can be viewed on Funi's video portal. By March 2010, all of the first season had been released on DVD - split into two "seasons" for whatever reason. In February 2011, Funimation announced that it has licensed further seasons and will continue the dub. However, production came to a standstill after the completion of their third, and as of February 2013, the show is "now on hiatus" — though, another, more faithful English dub provided by the Animax network is still going strong in a few select countries of the series' birth continent. Nineteen of their efforts (episodes 104-130) can be viewed here.Adding to the multimedia franchise, Namco Bandai released an RPG adaptation using the Tales engine in March 2010.Now has a Awesome Music page in progress.
Also from Saburo in episode 298, a reference was made to Akira Ishida's role as Xellos from Slayers, with Saburo using his catchphrase, "That is a secret!"
It is particularly amusing to read the manga with Giroro speaking with Vegeta's voice.
And, of course, the actual dub has had fun with the fact that Giroro is in fact voiced by Christopher Sabat, who was Vegeta (and Piccolo) in DBZ. Giroro hoping Keroro will turn into a Super Saiyan, Giroro mentioning the Fusion Dance in the very next episode...
In episode 29, the octopus-like creature used to frighten the newspaper club in the manga is replaced with an obvious Ryo-ohki reference (Ryo-ohki being one of the first characters voiced by Etsuko Kozakura).
Pururu's birthdate is exactly the same as her voice actress.
Despite the lack of a rival character being introduced, episode 282-B, bears a great deal of resemblance to the 3rd episode of the anime Mirumo de pon (the titular character of which shares Tamama's voice actress); Early in the episode Tamama taunts a dog and is consequently bitten when it turns out the dog is unchained, in the same way that Mirumo taunts and is subsequently chased by a cat that is unchained by Yashichi. Additionally near the end when Tamama unleashes pet up Tamama impact fury on the robotic flies that caused him to drop the over-ripe Keronfig he was trying to eat (and everyone that was in the same general direction as said flies) closely mirrors the savage beating that Yashichi receives from Mirumo as punishment for ruining his cake.
In the dub, Lavie's TV show is called "Gunbringer Girl", and it's described as being about "a cyborg child assassin who always brings her gun with her everywhere." Mois (Carrie Savage) thinks the title and the premise sound familiar - her actress having had a minor role on Gunslinger Girl.
For beings who destroy planets for a living, the Angols are pretty damned nice.
Alien Among Us: ...well, that's kind of the idea. There are other aliens on Earth besides the Keroro Platoon, though.
Aliens Steal Cable: Even in the original, Pekoponian media saturates the lives of aliens, though in the dub this is exaggerated. There's even a Galaxy Quest reference, where the Keronians believe Star Trek episodes are the actual documented voyages of a real Enterprise.
All Love Is Unrequited: Momoka likes Fuyuki, Chiruyo likes Fuyuki, Alisa likes Fuyuki, Fuyuki likes... being nice? Natsumi likes Mutsumi, Giroro likes Natsumi, Koyuki likes Natsumi, Tamama likes Keroro, Mois like Keroro, Keroro likes his Gundam models, Bariri likes Pururu.. and the list goes on, including situations involving one shot characters.
Played straight to hilarious results in episode 320. When Pururu finally falls in love with Bariri, Bariri is the one who becomes disinterested.
Anticlimax: All through the Episode 101-103 arc, it was being set that there was going to be a huge epic showdown between Dororo and Zoruru. Of course, right when it was going to begin, Dororo revealed that he didn't remember Zoruru, and well, Zoruru just left. HE JUST LEFT.
Events in Volume 17 and Season 7 correct this error.
This gets played for laughs too, several times. In the fourth movie, the climax sees Keroro willingly undergoing the ritual to evolve himself into a dragon, and Shion starts reciting from the spellbook, as Keroro starts to glow and the music slowly builds up — so slowly that Keroro catches a cold first.
Artificial Limbs: Zoruru, who not only has a robot arm and leg, but an entire half of his body and head too.
Art Shift: Momoka tends to commit this during her plans to get closer to Fuyuki, who appears in a deliberate shojo manga art form, sometimes lampshaded by the Narrator. Similarly with Tamama turning psychotic.
Ascended Extra: In the manga, Sumomo was a character from a one-shot side story loosely connected to the main comic. In the anime, she was remade into an alien Idol Singer who was taking an impromptu vacation on Earth in her first appearance, and eventually became a recurring character. Interestingly, the show seems aware of this, as some characters only appear between long stretches of episodes, prompting the narrator to cheerfully jog the viewer's memory.
Asleep for Days: Happens to Keroro in the 100th chapter, "The Frog That Lost New Year's", after partying a little too hard on New Year's Eve.
Ass Kicks You: In episode 175, Fuyuki, Keroro, and Giroro shrink so they can swim in a kiddie pool. Everything goes fine, until Natsumi and Koyuki show up and jump in the pool. Fuyuki and Keroro get tossed around and generally battered...but Giroro? Natsumi ends up sitting on him, complete with crunching sounds and poor Giroro groaning in pain.Ouch.
Author Avatar: One of manga editor Aki Hinata's employees is called Yoshizaki-sensei, referring to Mine Yoshizaki (who used to work with Futari Ecchi creator Katsu Aki). This character goes on to appear onscreen several times, including one scene in the third movie where he's enthusiastically sketching Dark Keroro's flying fortress.
Badass Mustache: Paul. The dub exaggerates its size and importance frequently; Natsumi said she could see it and nothing else when Paul approached the Hinata house in a helicopter.
Badass Normal: Natsumi, Aki, Paul, both Momoka's parents. Koyuki and the ninja clan are a borderline case.
Bad Export for You: A very minor case. It has nothing to do with the localization, but rather the Region 1 DVD release by Funimation. The company's "Season 2" releases contains episodes 27-51, which are actually part of the original Japanese "first season". The actual "Second Season" began with episode 52 in Japan (as read on the covers for the Region 2 DVD's). It's unknown why Funimation decided to do this.
Seasons generally run 24-26 episodes, and Funimation didn't take into account what the Japanese used, even though they do for other long-running shows.
Also, Funimation has mentioned a few times that they only licensed those first 51 episodes (despite implying earlier that they had acquired up to around episode 102). Since everyone already knew that this is a show lasting multiple seasons, Funimation may have decided to just split the difference and call it two seasons to be done with it.
But now Funimation has decided to release the next 26 episodes (eps.52-77), and are calling it "Season 3", which has managed to reopen this argument over semantics.
Baseball Episode: Several variations, including a soccer episode, a tennis episode, a general winter sports episode, and a swimming episode. There's even one episode where the characters played Yukigassen, the organized sport version of snowball fighting!
Beneath the Earth: Side 6, an underground city that acts as refuge for all alien immigrants on Earth, but otherwise looks exactly like any street-level environment. Turns out that not only is it really a massive space battleship buried underground, but it combines with Side 1 through 5 to form a Humongous Mecha!
Berserk Button: You hurt Natsumi, Prepare to be filled with bullets by Giroro.
Also, Tamama/Momoka are Berzerk Keyboards!
And DON'T EVER break any of Keroro's Gundam models! In the dub this extends to all mech-related merch; he once punched Tamama for breathing on his Voltron playset.
And when some visiting aliens broke some of his models:
Keroro: 'What flavour is your blood?!'
The "animal animalizer" episode featured some crows who attack Sarge after he mentions he's into Gundam - crows hate Gundam, since everybody knows Macross is where it's at!
Don't ever hurt Keroro in front of Mois. She's got the power to destroy the entirety of the planet in her hands (although she does downsize her power when it comes to teaching those who harm Keroro a lesson, thankfully!)
Beware the Nice Ones: It is very, very difficult to get Fuyuki pissed, but God help you if you do. Even Natsumi becomes terrified of him.
Angol Mois can qualify, considering she can quickly go from not hurting a fly to trying to destroy the world and back again.
BFG: Garuru's sniper rifle is at least 5 times larger than himself.
BFS: In the first chaper of the Musha Kero saga, the first of the five crystals our heroes recover turns into this, just in time to grant Keroro a Crowning Moment Of Awesome.
Big Damn Heroes: To be expected whenever the storyline goes into full-blown action mode. Of special note is the Garuru Platoon arc, where Giroro is appparently shot down in combat, but later rises from a lake a la EVA-02, and blasts into the captured underground base by RIDING A BARRAGE OF MISSILES.
Episode 133 has a rare case of Tamama leading the Big Damn Heroes moment to rescue practically everyone else from Alisa Southerncross.
The fourth movie has Aki doing this in a Citroen 2CV.
Big Ol' Eyebrows: Keroro has so much determination every once in a while, he grows giant eyebrows to display it.
Biker Babe: Aki and her motorcycle can outrun anything. ANYTHING. It seems Fuyuki inherited just enough of this to outrun alien missiles on a bicycle in the second movie, BEFORE activating the Nitro Boost.
Birds of a Feather: Arguably, each of the Keroro Platoon is perfectly matched up with another major character. Keroro to Fuyuki, Tamama to Momoka, Giroro to Natsumi, Kululu to Mutsumi, and Dororo to Koyuki.
Fuyuki mentioned in the manga that Tamama and Mois were like Birds of a Feather since they both didn't overthink their actions when trying to save others or going Berserk.
Bland-Name Product: Aki's place of employment, Kadoyama Shoten Publishing, based on the real-life manga publisher Kadokawa Shoten, and the animation company "Sunirase", based on Sunrise, the company that animates Keroro.
The Gundam ripoff seen occasionally, Dangale, is another example of this trope, but not to Gundam itself. It looks virtually identical to a real life Gundam knockoff called Gungal (And a more proper romanization would be "Dungal"), only with a different name and slightly goofier proportions. The manga actually used the Gungal name itself, rather than Dungal/Dangale. Hilariously, one of Keroro's model kits actually was released with a miniature Dungal as an accessory.
Bleached Underpants: Sort of. Space Policewoman Poyon-chan began her career in one of Yoshizaki's doujins, wearing only her UFO skirt and three small adhesive stars. Yoshizaki himself is much in demand as a pin-up artist (see his book Mine Blue for examples).
The Blind Leading the Blind: happens whenever our heroes get to explain things about Earth to other aliens. Episode 291 in particular involves Nevula getting the wrong idea about the onsen from Giroro and Kululu.
Book Ends: The third movie open with a recap of important anime scenes like Keroro being discovered by Fuyuki and Natsumi; then ends with Dark Keroro being discovered by Space Fuyuki and Space Natsumi.
Bratty Half-Pint: Karara, Chiroro, Tororo, Taruru (to some extent) and Sumomo (in the manga).
Through flashbacks and Kululu's age manipulation beam gun, we learn that Fuyuki used to be the brattiest of them all.
Brilliant, but Lazy: Kululu — as shown in the Nintendo DS game Keroro Gunsou: Enshuu da Yo! Zenin Shuugou, he can't be bothered to get out of his seat for the leg race minigame, even when a giant spiked steamroller is chasing him. (Why, when the seat runs for him?)
Cannot Tell a Joke: Koyuki is like this in the English dub of episode 18, judging by her failed attempt to tell the joke about The Aristocrats. When they return to the beach a year later to compete in the comedy contest again, she's improved a little — she can now tell a joke, but her material, featuring "walk into a bar" jokes, is extremely stale.
Canon Discontinuity: In a story of the 2nd year of the anime, Fuyuki and Keroro visit various famous ancient locations around the world, trying to find signs of alien artifacts. They turn out to be either toys or domestic utensils built by ancient aliens, completely useless for the invasion. However, later manga chapters, TV episodes, and movies presented completely different origins and functions for those locations, ignoring that episode.
To be fair, that episode actually ended with a Hand Wave disclaimer.
A recent ep details elementary-school Momoka's original Crash into Hello with Fuyuki, who didn't see her coming as he was busy reading a book... wait... wasn't he the Bratty Half-Pint at this time?
The bratty Fuyuki is younger than the Fuyuki that Momoka met. Although the anime changes the events slightly to make Momoka and Fuyuki meet earlier than in the manga version of the story (from one week to at least several months or even years before), the Fuyuki that she meets in the anime still is older and taller than the bratty one.
Canon Immigrant: Several characters later in the series appeared in the anime before the manga, most notably Pururu and the casts of the 2nd and 4th movies. Of course, all those characters were originally created by Mine Yoshizaki anyway.
Captain Ersatz: Baio and Ouka Nishizawa. In an early episode, Baio and Paul fought using techniques similar to Street Fighter characters Ryu and Ken while talking about their past rivalry. That short scene could be seen as a simple Shout-Out. However, when Ouka finally appeared, it was revealed that, when they were younger, the couple closely resembled Ryu and Chun Li and met each other in a fighting tournament which, in the anime, featured other Captain Ersatzes of the Street Fighter II cast. Even in the present, Ouka's outfits are variations of Chun Li's, and both Ouka and Baio mostly use techniques based on Ryu's and Chun Li's. Paul Moriyama shows similarities to both Ken (flashbacks) and Akuma (in the present, only after Ouka's introduction), so he isn't a Captain Ersatz of any specific character.
There was also the briefly seen, but also the most obvious example, Eddy Honda to Street Fighter's Edmond Honda. Eddy Honda was a sumo fighter competing in the street fighting tournament and was defeated by the younger Ouka. He even fought in a location resembling the actual Honda's Street Fighter II stage and had the same voice actor as Edmond Honda from the Street Fighter II animated movie.
In-universe non-character example - the Nishizawa radio tower to the Tokyo Tower. It helps that the NPG can afford to build a new one. Which they've done a few times.
Although the Nishizawa radio tower takes the roles usually given to the Tokyo Tower, its design is actually taken from the less famous Skytower Nishitokyo.
Chekhov's Skill: The Great Resonance, which the Keroro Platoon discovers completely by accident in episode 155, is used to power up the God Keron's final attack against the Keromet in episode 203.
The Chew Toy: Keroro's regular failure to complete his plans of world domination or even his household chores result in him getting grabbed by the head, smacked, punched, shoved into the wall, kicked across the room (gooooaaaall!!), and otherwise getting abused by Natsumi. Lampshaded in one 'flashback' scene where Keroro throws in a few Japanese torture sequences that never really happened...
Conspicuous CG: Keroro's ceiling fan. Seriously, how is THAT the only thing?
Most of the closing credits sequences utilise cel-shaded CGI.
Which makes it into the show proper for most of the Chibi Kero episodes, and the entire short film "Secret Of The Kero Ball".
Contrived Coincidence: In episode 112, it's revealed Kululu had a second Reality Pen, the first of which he gave to Saburo. The Platoon members go into Kululu's memories to see where it ended up, and it's revealed that he loses it during the events of episode 2 and that it was destroyed by the Tamama Impact Tamama fired towards the end of the first half of episode 2.
Episode 37 has a series of coincidences that end up saving Keroro and company from a rampaging dinosaur.
Crash into Hello: In Episode 2, Momoka bumps into Fuyuki intentionally in order to get an excuse to talk to him. A flashback chapter in the manga shows this is, in fact, how Fuyuki and Momoka originally met.
Creepy Monotone: Kululu, who gets inexplicably high pitched when he gets particularly excited about something (usually terrible or destructive), which actually makes him even creepier.
On the other hand, Mutsumi and Omiyo appeared in Seven of Seven after debuting in Keroro's manga. However, that was actually their first animated appearance too.
The Keroro manga had frequent cameo appearances by Fubuki, from Arcade Gamer Fubuki, and her best friend in the background of several scenes. Eventually, there was a full blown cross over chapter where Fubuki beat Keroro in an arcade game. Fubuki only makes a single brief background cameo in the anime.
In the Fubuki anime, one of the finalists of the videogame tournament which is at the center of the story looks suspiciously like Kururu in a Pekopon suit.
Natsumi and a Keroro plush had guest appearances in the Arcade Gamer Fubuki manga. Keroro plushies are also seen in the anime.
'Space X Jyubei', main character of an obscure manga by Mine Yoshizaki, had a guest appearance during the chapter which introduces Dororo in the manga, listed among the aliens on Earth. He was absent from the anime version of the story.
In the single volume of the 'Space X Jyubei' manga, the last chapter is actually a complete crossover with Keroro, featuring not only Keroro, but also Fuyuki and Natsumi in main roles.
Angol Fear, Mois' cousin, debuted in Soul Calibur IV, but her backstory always referenced Keroro, mentioning Mois, who'd come to Earth after her. She eventually would go on to appear in the Keroro Gunso manga itself.
Keroro plushies and toys are seen in Lucky Star, and there's even an episode preview where Keroro, Tamama and Giroro take control of the narration.
Crouching Moron, Hidden Badass: There is a reason Sgt. Keroro is the leader even though he appears to be a fool. Threaten (or worse, actually hurt) his squadmates or his adoptive family, and there's no force in the universe that will stop him, as the Garuru Platoon found out. Or just get him too wet. See Berserk Button far above.
Fuyuki has a bit of this too — in several instances Sgt. Keroro pushes him too far, he gains a Battle Aura and a shadow covers his face, then the manga cuts over to a terrified Keroro and a cheerful Fuyuki. The first time this happens he actually stops the otherwise unstoppable Keroro described above. See Berserk Button, pretty close above. Also Beware the Nice Ones, far above.
In one chapter of the manga, the platoon goes way too far by converting some old Children's Day carp flags (which Fuyuki considered a family heirloom) into invasion weapons. Fuyuki snaps, prompting Natsumi to genuinely panic, and Kululu quickly zaps him with the age reduction beam. Child!Fuyuki promptly takes charge of the invasion.
Crowded Cast Shot: Several events in later episodes routinely reunite at least one member of each alien race shown in the series up to that point, although most only return as background cameos.
Episode 296 is the biggest example in this series. The first half, featured piles of letters and cards sent by old minor characters. In the second half, there was a competition involving one member of every alien race shown in the series up to that point.
Darker and Edgier: Subverted. In the 7th season, when half of the series moved to a late night timeslot, called Keroro Gunsou Otsu, there was an entire story about Keroro becoming "Keroro of the Night", and so, "Adult, Dark and Dangerous". However, as it turns out, he was no different from before and he's defeated as usual.
The late night stories generally have more Fanservice and Continuity Nods than the 7th season's morning stories though, but they aren't really darker.
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)
Disappeared Dad: Where is Mr. Hinata? He seemingly returns at the end of the anime, though the reason for his unspoken absence remains a mystery.
According to the wiki, it says that it's because of his constant traveling, which is more than likely attributed to his also mentioned fascination of global mysteries, such as that of Easter Island's Moais.
Don't You Dare Pity Me!: In the manga when one of Tamama's attempts to discredit Mois not only ends in failure but results in Mois trying to console him without knowing what she is consoling him about.
Drives Like Crazy: Aki Hinata has a car as well. She is already known as a terror on the mountain roads in the series and is implied to have traversed miles of implausible terrain in a Citroen 2CV in the fourth movie.
Dub Name Change: Averted in the released version, but apparently part of Funimation's original plan for this show was to eliminate the last syllable from the aliens' names (Keroro becoming simply Kero) and have Earth be known intergalactically as "Planet Wuss" and humans as "Wussians". Funimation likely abandoned this due to negative feedback on the changes.
Although they change one name... sort of. Giroro's cat doesn't have a name at all in the original (everyone calls her "neko"; "cat" or "kitten"), but the dub calls her Miss Furbottom. In addition, Dasonu*Maso becomes the Dance*Master, because the pun doesn't even sort of work in English.
Broadcasts in languages other than English sometimes went rather farther than Funimation's dub did; Keronians tended to keep their original names but the human characters were occasionally renamed to fit with the language of the dub.
Earworm: Too many to count. However, "Afro Gunsou" seems to have a special place stuck in people's heads.
Just go talk to people and not add "De Arimasu" mentally to every statement. I dare you!
The 2nd Ending Song. It's impossible to not sing along with "Kero".
Eldritch Abomination: An enormous black hole dragon, composed by milions of smaller negative matter dragons, which appears in one of the show's final episodes (7th season), easily slaughtering the combined force of the Keronian army. Of course, the series doesn't end with it destroying the universe. So, somehow, it's defeated.
Everything's Better with Princesses: The second movie, where Natsumi became a sea princess. Keroro's hairbrained idea to get her back involves dressing the rest of his troops as princesses. And he tries it again in the third movie.
Momoka gets recast as an actual princess in the Musha Kero storyline. She is The Ojou, after all!
Keronian females tend to have cat-ear-like protrusions on their hats (Pururu in particular gains these as an adult).
Evil Counterpart: The Garuru Platoon to the Keroro Platoon in Episodes 101-103. Taruru to Tamama, Garuru to Giroro, Tororo to Kululu, and Zoruru to Dororo. Strangely, Keroro did not have one. Also done in the Third movie, with Shivava to Tamama and Doruru to Giroro. Dark Keroro counts, but he's more of an Evil Twin to Keroro.
Expy: There are many characters and inventions which are obvious homages to other works, from the more well known ones like Wettol King to Iron King and Ultraman or the Pekopon Invasion Machine resembling a green Gunbuster to the less well known and one shot ones, like the Abilika group from a 5th season episode to Time Bokan's trio of antagonists and their successors.
In-universe examples: Dasonu* Maso is the unabashed bootleg version of Dance* Man (see Ink-Suit Actor below).
Yoga and Cyclone to Street Fighter's Dalshim and Zangief (and, in this later example, Ouka actually calls them rip offs and compares them to the original ones, or their unseen Captain Ersatz versions, whom she had faced before).
Alongside those two, there's one to Guile, in a rather absurd way. Oka actualy complaints about his Hairstyle not comparable to the original, and lie on the ground while the Guile expy are charging for Sonic Boom or Flash Kick, just like in the game.
Let's not forget Saburo who is also an expy of Kaworu, considering that the first time he visits the Hinata household, the ode to joy starts playing and everything is pretty clear from there.
The second ending theme song gives you the mother in a bikini as a special reward for sticking around for the credits.
Fake Shemp: Many minor characters, like aliens created for specific episodes, return later in minor roles. Unless they were voiced by one of the show's main voice actors, this usually means they either get random voice actors replacing them or just appear mute. This happens more rarely with minor human characters, but there are still some examples, like Natsumi's and Fuyuki's teachers in later episodes.
Sumomo is probably the most obvious example. The last time her VA returns to do her character's voice is in the beginning of the third season. Afterwards, Sumomo only makes minor silent cameos or uses old audio.
There's also an example with Danceman in the 5th season. He's shown in a far away shot of a concert, which uses stock audio.
Fantastic Voyage: In episode 10, Keroro's mouth becomes infested with microscopic, cavity-causing aliens, and a good chunk of the rest
of the cast (including a robot duplicate of the sergeant mentally controlled by Keroro) shrinks down and enters his mouth to fight them off.
Fantastic Racism: There's a reason they couldn't get away with calling Earth Pokopen in the anime. Though honestly, Pekopon sounds about as evocative of the original as saying the "n" word with the "er" replaced with "a".
For those who don't know, "Pokopen" was a derogatory term for China and the Chinese before and during World War II. It's considered extremely offensive today and usage of the word on Japanese TV is banned.
Forgotten Birthday: Keroro does this to Natsumi in one episode, while Fuyuki insists that Natsumi wouldn't enjoy it. Much to his chagrin, he finds his sister not only has a good time at the party, but completely fell for the Forgotten Birthday ploy.
Forgotten Phlebotinum: The Kero Ball and Angol Mois's Lucifer Spear gets used less and less each season. This gets lampshaded in the third movie - both items are lost at different points, but recovered from the wreckage during the end credits.
The 7th season of the anime attempted to reestablish the basic characters and setting of the show. As a result, both of these elements come to the forefront again. There are 3 episodes with the Keroball in the center of everything just in the first half of the season. That's more than in all of the first season!
Four-Temperament Ensemble: Keroro and Tamama are Sanguine, Giroro is Choleric, Kululu is Phlegmatic, and Dororo is Melancholic.
Funny Afro: Anyone who survives an explosion will have their hair fried into this, with bonus sideburns and soul patch, in Keroro's case.
A variant in episode 294: Paul's Mobile Shrubbery camouflage includes a massive green afro resembling a bush.
Gag Dub: Funimation pretty much took the same approach as they did with Shin Chan for this dub. That said, it leans a bit more towards Woolseyism (if with a side order of Lull Destruction) than most Gag Dubs, staying faithful to the main plot of each episode, while changing up references and adding new jokes.
Funimation's original dub represents this trope much more accurately, making the current dub look like the original Japanese version in comparison. Unsurprisingly, fan response was mixed.
On the Real Life front, this show is apparently extremely popular in France.
Getting Crap Past the Radar: A little-known gesture of implied rape in Japanese culture involves the Shogun grabbing the waistband of his consort and ripping it off so hard that she spins several circles and falls on the bed with her clothes splayed open. The second movie actually turns this into a running gag... with Giroro as the consort.
This gem of a line from the dub, which makes sense in context in case you're wondering: "This DNA spilled out of your sack!"
Another line from the dub, when Keroro becomes a teacher: "My name is Hugh, but you can call me Mr. Jass".
In the same episode, Tamama and Giroro play his students. Their names? Jacques Strap and Seymour Butz. Not as subtle but still counts. Also one of the students remark, "Their names combined are Butt Strap!"
"I can’t handle Natsumi like this! She’s too womanly! I need a cold, cold saltwater shower!"
One that dances the line between subtle and downright egregious is in "Lost in Transportation", uttered by Keroro as he caresses his long-awaited KRRSP: "Oh, baby, what took you so long to come?"
Netflix has the dubbed version of the show under children's TV, making typical words like "bastard" in the dub more of this. Sure, it is categorized under 8 to 10 and 11 to 12 (tween audience), but still...
In episode 74, there's a mini-episode called "All Night Wrong" where Momoka believes that Fuyuki is having sex with Angol Mois in his room after spy reports say that they haven't left Fuyuki's room all night and Tamama remarks about them in the dub "totally making out and...stuff". Turns out, Fuyuki is just helping her with her English, but still, how does this get past the radars of Netflix and FUNimation, both who assign it a simple PG rating? Momoka even remarks, embarassed for barging into his room, "Oh, you're dressed, that's good." Also, in the beginning of the episode, Fuyuki remarks in an out-of-context conversation "Um...are you sure you're ready to do this?" to which Angol Mois replies "I guess...I just want it to be right, you know?"
Grand Theft Me: Thanks to a special Gashapon machine. In the anime, the first time, it's used by Keroro to steal Natsumi's body, but the situation ends up closer to "Freaky Friday" Flip when he is dragged to help her classmates. The manga's story turned out differently though. Either way, it seemed like a one-off item, but it returned in the 6th season. Keroro's mother disappears with Natsumi's body and even convinces Giroro to go on a date with her. There were also incidents involving Momoka and Keroro and Tamama and Fuyuki, when Tamama decides to use Fuyuki's body to approach Keroro and even attempts to kiss him... although he made a mistake. In the later episodes, the voice actors stay with the bodies, only following the personalities for internal monologues.
Engrish: Once scene involving Tamama's Jealousy Ball has its proper Japanese name, 'Shittou Ball', written in the background in English — only it's spelled Shit Ball. Seriously.
On a less hilarious level, Momoka's swimsuit from the first beach episode is "Qute".
The dub invokes this in episode 4: "Buubii Torappu?"
"I know that says 'Warnig' but I'm pretty sure they meant 'Warning'."
Fuyuki has a sign on his bedroom door reading "Winter", which he has also used as a codename. Natsumi was, of course, "Summer."
Related is the Mois-Momoka-Natsumi group "More Peach Summer", the name of which vaguely obscures the identity of its members by hiding them behind English words relating to their names.
Gratuitous Spanish: Angol Mois in the dub, probably because to a western viewer her tan complexion immediately suggests Latin heritage.
And then lampshaded when she stopped doing it. Well, okay, she doesn't do it as much anymore at least, but "stopped" is an exaggeration.
Green-Skinned Space Babe: Every female alien if they are not from the keronian (or viper) race. The keronian females can change into human females though and do this VERY often. Did we mention this show/manga is created by a GUYyet?
Hero of Another Story: Yamato and Kapu. Yamato was a kid around Fuyuki's age who befriended a kappa-like creature similar to Keroro, who took he and his friends in many adventures. When Fuyuki meets him though, Kapu had disappeared, although his friends still hoped to meet him again.
In the manga, it's directly lampshaded by Fuyuki writing a report afterwards where he talks about how he realized, with that incident, that there are other stories like his going on in the world, which doesn't spin around him after all.
Homage: Out of all the shoutouts to Mobile Suit Gundam, the third movie in particular offers what may be the strongest homage yet, with an actual Gundam being used against the enemy. Keroro's rendition of the theme song just adds to it.
The 4th movie starts out with Keroro dresing up as the Zeta Gundam and ZZ Gundam, then takes advantage of the retro setting of France to homage ∀ Gundam. Case in point, Pierre's uniquely shaped moustache, and the presence of antique coat-of-arms that resemble known UC mecha.
Honorifics: Keroro is especially fond of using honorifics with his adoptive family, applying military-equivalent ranks to each member. He uses "dono" for the family members in the anime, and calls Aki "Mama-dono". Mois calls Keroro "Oji-sama" (Uncle).
Well, at least, that's what the Angol clan considers humanity to be in the manga, sensing various evil thoughts throughout the world and even being able to count how many sins are happening on Earth in a specific moment. This would explain why the Angols seem nice, despite their destructive aims.
Also in Soul Calibur 4, which features Angol Fear, Angol Mois' cousin who'd go on to appear in the Keroro manga later. Her story suggests the Angol race thinks Humans Are Bastards, and possibly the reason they want to destroy Earth is to save the rest of the Universe from that corruption expanding; Ultimately, Angol Fear observes that there are many innocent humans, and leaves it up to Angol Mois to decide whether to destroy Earth or not.
Humans Are Special: It's hinted in one arc of the manga (the World's Tiniest Invasion: Lost Episode IIRC) that humans have an absurd level of mental potential, and that Keroro's contact with them has put his own potential far beyond that of the average Keroronian, which still leaves him far below a human's level.
Hyperspace Arsenal: Giroro's weapons are always summoned from nowhere via Keronian tech. In the third movie, Kululu's computer system is hacked and Giroro is left without his heavy arms for half of the movie.
I Call It Vera: J. Michael Tatum has admitted to naming Dororo's katana "Stephen". This made it into an episode when Dororo broke his sword against an indestructible spaceship hull and cried its name out in grief.
An Ice Person: Koyuki has some ice-related ninja moves, as her name would imply. Also Yukiki, who was a snowman after all.
Identical Grandson: After being zapped with Kululu's "Midlife Crisis" gun in Episode 9, preadolescent Aki is shown to look very similar to Fuyuki (but not close enough that Funimation's dub could resist lampshading it). A later episode involving time travel reveals that teenage Aki looked a lot like Natsumi — except for the hair color and the glasses, of course.
Fuyuki's son shown in a brief glimpse of the future at the end of the 6th season looks basically identical to Fuyuki's Bratty Half-Pint younger self.
Identical Stranger: the Musha Kero saga taks place on a planet full of people resembling our heroes' friends. Their actual characters range from disturbingly similar (Fuyuki, Momoka) to completely different (Natsumi, Saburo) to something from out of left field (Mois.)
Animax's little-known English dub of the show—it was only seen in Asia—preserves this tic by having Keroro's voice actress (yes, they kept his cross-dressing voice too) say "Sir, yes sir!" after the title.
The Idiot from Osaka: Keroro, but without the accent. Whenever he has one of his money-making schemes he gains one, and eats takoyaki.
I'll Never Tell You What I'm Telling You: Early in the second season Keroro uses a robot copy to skip out on the invasion meeting and the copy is found out. When pressed for information Tamama insists that he'll never tell them that Keroro used the robot so he could go see the Java Risers show at the amusement park
Dororo's mother can battle berserk security robots with frying pans.
In the episode that introduces Giroro, Natsumi busts right through a massive array of tripwires, plastique, and claymore mines with just a leek. The finishing blow is delivered with a bookbag to Giroro's head.
Inconsistent Dub: Tamama Impact is usually referred to by some variant of "Crazy Rage Breath", but occasionally they still call it Tamama Impact. Kogoro's transformation word also flips from "Attach-O!" to "Adhesion", the literal translation of the Japanese.
Invisibility Cloak: The Anti-Barrier, or the system the Keronians use to become invisible to anyone other than a select few, like the Hinatas.
It's explained that very curious people (like the mangakas in the deadline arc, and the Hinatas early on) can see straight through it, but then it says this is how Natsumi and Fuyuki saw the Sergeant to begin with... yet Keroro had forgotten about the anti-barrier at that point. Someone slipped, or maybe Keroro's just a moron.
Natsumi is a total jerk toward Keroro. Yes, she hates the fact that a platoon of aliens intending to take over the planet is living with her, but she constantly abuses him, both verbally and physically, at the slightest provocation.
Keroro too in the first eps, but than he became a bit of a Butt Monkey with little lines.
Occasionally Keroro comes off as this, except he's not so much a jerk to begin with as an annoying, mooching houseguest. However, he does tend to do the right thing when all the cards are down to crisis point—right by human perspectives; his own race may think differently.
Later, there's Shivava, in the 3rd movie, and Orara, in the 7th season, who are, respectively, Expy of the Monkey King (with a bit of DragonBall's Goku thrown in) and of Dragonball's Goku himself. Both of them had Kamehame Hadokens and a Battle Aura. Orara was even voiced by Goku's original voice actor.
Kid from the Future: One episode has Fuyuki and the platoon dragged into the '80s, where Fuyuki meets young Aki.
Last Episode New Character: There were three of them in the last episode of the 7th season shown throughout all of Japan (257. 258 had an initial limited Tokyo-only run), two who probably will return later if the anime continues. The characters were the supremer commander of the Keronian army, an invasion AI called DK-666, and also Haru Hinata, Fuyuki's and Natsumi's absent father. The last one basically only had a cameo appearance though, and his face wasn't even shown.
Lawyer-Friendly Cameo: Very common in the manga, but the anime has significantly less of them. Aside from Gundam characters mentioned by Keroro, the cameo characters in the anime are usually redesigned, even if only for actual silent cameos, and renamed, if they actually have credited speaking roles, basically becoming Ersatzes. There are a few rare straight examples though, like the Great Mazinger briefly appearing in the middle of a war zone and in a radar during episode 145-A, without any redesign, where different parts of it were visible in the different scenes (legs in one scene, silhouette in another).
Lotus-Eater Machine: Episode 3. A variant appears in Episode 135, in the form of Kululu's beam gun invention that causes Keroro to dream that he's lived his entire life as a grain of rice. He wakes up with an epiphany.
Episode 267 features one that started out as a virtual reality headset, until Keroro himself gets hopelessly addicted to one... and imagines himself successfully conquering Pekopon at long last.
Lovecraftian Superpower: Subverted, as Alisa's assumed to have this ability at first, but it's really due to her "Daddy", a shapeshifting symbiote that lives on her head.
Made of Rubber: The real reason Keroro survives Natsumi's abuse. Keronians are shown to be particularly flexible, never needing more than bandages and maybe a crutch for their injuries (unless the plot requires otherwise), to the extent that the human children can survive very high falls by landing on Keronians.
Mars Needs Women: Giroro's crush on Natsumi, and a reversal in Moa's crush on Keroro. This is made ironic in the former's case when he reviews a pre-invasion press conference wherein he violently insisted he would under no circumstances fall for a native woman.
Partial subversion in the second movie, when alien prince Mero kidnaps Natsumi to make her his princess. As it turns out, he's just a child, and Natsumi winds up as his surrogate mother instead.
Mascots Love Sugar: Tamama, to the point that in one of the final episodes of the first season he is diagnosed with high blood sugar and in one of the first episodes of the 4th season when he is told that he is at risk for diabetes.
Keroro comes from "kerokero", the Japanese onomatopoeia for the sound a frog makes.
Tamama comes from "otamajakushi", which is Japanese for "tadpole". It can also be linked to "tamatama", which means "unexpected" (referring to his fierce mood swings).
Giroro comes from "girogiro", which means "sharp-eyed".
Kululu comes from "kurukuru", which means "spinning" or "wound up" (referring to his whorl mark and the spirals on his Nerd Glasses). It can also be linked to "kuru", which means "hunchback" (referring to Kululu's stooped posture).
Dororo comes from "doron", which is onomatopoeia for a Ninja vanishing. It can also be linked to "dorodoro", which means "syrupy" (which describes Dororo's sentimental and emotional tendencies) Dororo is also a classic samurai manga my Osamu Tezuka, though this may not be relevant in the etymology of Dororo's name.
Medium Awareness: Aki, being a top manga editor, is primarily responsible for this. Also, the Narrator can pinpoint the episode numbers of recurring events and character debuts on demand.
Dasonu*Maso/The Dance*Master mentions in his debut ep that if he leaves, the episode will be over (because there won't be anything to provide conflict)
Merchandise-Driven: Inverted here - it's Keroro's love of Gundams that earned them Bandai as its merchandising arm. The KeroPla line of plastic models features Keronian characters and mecha all compatible with existing Gundam models.
And on Keron, the platoon is a super duper popular cash cow... but they didn't actually know this until they got letters from Keronian kids on New Year's. Somebody's really rich, but it sure as Hell isn't them.
It's parodied in episode 10 of the anime (at least in the dub), where an armored vehicle is introduced just to add it to the toy line.
Keroro: It's so roomy!
Giroro (in monotone): Yes for action figures, and toys.
Mildly Military: Done intentionally, the squad is lazy and incompetent, and their only oversight is the reports Keroro has to send back to his superiors, in which he lies outrageously.
Mobile-Suit Human: The Keronians run around in these when they need to be seen in public.
Kululu's female Pekoponian suits (to date, Kululuko and a faux-Natsumi loaned to Sumomo) fit more closely, placing the Keronian pilot entirely within the torso instead of leaving the head exposed to allow for a more realistic human appearance — despite being quite unnecessary (see Paper-Thin Disguise below).
Mooks: All the members of the Shurara Corps aside from Shurara himself.
Multiple Endings: The "segmented endings" variant. They aren't alternate takes, just more and more complete versions of the series. The show's 7th season aired in different timeslots, with different running times in different timeslots. In order to satisfy people who couldn't watch the longer version of the show, the last 3 episodes of the series all ended up being different types of ending stories.
Mundane Utility: Keroro sometimes elicits Keronian technology to complete his chores. A non-technological example would be Koyuki whipping out her ninja moves to do perfectly normal things, like Bunshin no Jutsu at the fashion store to try on five outfits at once. And the crescent end of the Lucifer Spear is revealed to be... a key for unlocking Moa's gigantic diary.
Narrator: As per Rule of Funny, the characters can hear everything the Narrator says (Natsumi asks him for fashion advice in one case), and finally the Narrator appears on screen (wearing a mask) in episode 40.
In the English dub, he frequently gets into arguments with the guy who writes the subtitles for the on-screen Japanese text (the latter often choosing to write insults rather than actually translating what's written).
Subtitle: "The narrator sucks!"
Narrator: Here's a caption: Bite me!
Hell, an ENTIRE EPISODE revolved around how Kururu got tired of the Narrator's comments, and caused even more mayhem. This causes all the characters to Blame the narrator
Kululu: "We're all tired of your complaining about how you hate the show, and how you're only here because of your gambling debts!"
later in the episode...
Narrator: Okay, someone remind me how this is all my fault?
Fuyuki: Because you hate the show?
The Neidermeyer: Keroro, sort of, his squad wavers between apathy and quasi-respect.
Never Bareheaded: All Keronians have hats, usually a long-eared one with their personal symbol on it. One episode involves a notorious Unreveal when Keroro switches to a baseball cap after his hat is picked up by a toddler.
The Musha Kero saga ends with one. Upon learning that civilians have been enslaved to unearth something in a mine, Kululu scans the area and finds an energy reading, and Keroro speeds up the excavation. It turns out to be an Eldritch Abomination.
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.
No Fourth Wall: Especially in the English dub, but there's hardly much of one in the original, either.
Nobody Poops: Averted normally, and taken Up to Eleven in one Kero Zero chapter. Basically, the mothership taking our heroes to Earth starts rationing all food and water when its onboard farms fail to produce any crop - our heroes wind up holding it all in for a week when they can't even use the toilet, then desperation forces them to dump it all all over the onboard farms, inadvertently fertilising the soil and allowing it to function again. They don't actually touch the food produced for some time, though.
Noodle Incident: It's mentioned often that Keroro was the most insane and violent soldier in all of Keron "in the old days", but the only times we see anything close to it is when Keroro gets drunk on moisture. A better example would be Keroro's own father, the "Demon Sergeant", rumored to be the most fearsome sergeant in the galaxy, but only appears on vacation in a Hawaii shirt and an easygoing attitude, at least on the surface.
No Sense of Humor: Giroro. In the dub, he describes himself as incapable of feeling joy.
Not Allowed to Grow Up: Even though every season of the anime features holiday and birthday specials and there are direct references to previous years, the human characters still keep their original ages and are still in the same school years. The same happens with Tamama, who still keeps a tadpole's tail and white face, even though Taruru, a Keronian younger than him, matured in the 2nd season.
Lampshaded by the manga, when Fuyuki said that he was "just 12(?) years old" in a later volume.
Irregularly contradicted by the anime itself, which is also the biggest offender due to the number of holiday and anniversary episodes. Paul, in Episode 92, mentions that Momoka's birth was commemorated 13 years ago, and Natsumi was said to be 14 in the second movie, which means that the entire cast aged at least one year. There are also various references to the Keroro platoon spending years on Earth and vague comments about the human characters getting older. However, official guidebooks still keep everyone's starting ages and school years as the only official ones.
The newest databook for the manga (as of volume 23) actually said that the human characters had aged one year since the start of the series, breaking away from the manga's previous references to the lack of aging of the human cast.
Not Me This Time: There's a rather sad example in one chapter; Keroro is expecting praise for doing a good job cleaning the house, but is instead met with furious accusations by Natsumi and Fuyuki of screwing with computer networks across the city, and has a nervous breakdown when they refuse to believe his pleas that he's not responsible. The real culprits turn out to be the Garuru Platoon, as a prelude to taking over the invasion of Earth.
Fuyuki is one by way of Fridge Brilliance. It's always stated that his interest is in the 'Occult', which being a grab-all term in itself means that Fuyuki has to be well-versed in world history, geography, archaeology, science, urban myth, maybe some astrology... It's at least stated that he's a brilliant detective on the side.
Actually, her theme repeats the words Nostra and Damus continouously. Although they're a clear reference to Nostradamus, they're also, individualy, actual words in Latin.
Also Shion Drakon from the fourth movie, the chant she uses to transform Keronians into Dragon Warriors is a little hard to make out, but it contains the word "draconis," meaning 'Dragon.'
One-Winged Angel: The fourth movie revolves around our heroes being forcibly evolved into giant dragons.
Only Six Faces: Keronians are a borderline case, since they come in a rainbow of colors and a few even throw out the humanoid build. Thankfully all Keronians have their own personal symbols.
On The Next Episode Of Catchphrase: "Sonna kotoyori! ("Never mind about all that!") Next week on Keroro Gunsou — (name of first story), de arimasu! (name of second story), de arimasu! Two stories! How about that! Gerogeeroo..."
The Other Darrin: Fuyuki's voice actress had to step down due to sickness and was replaced around episode 223.
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.
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.
Overprotective Dad: Nevulon is a fairly good example in episode 291 when he and Alisa Southerncross are separated at the hotsprings, and he goes insane with worry.
Palette Swap: It's used a lot in the anime for background Keronians, which generally share a few sets of generic designs (eyes with small irises, star emblems, hats similar to Keroro's or Kururu's, headphones included.
Later episodes also use it for random background aliens.
It's rarely used for humans, but, oddly, there's a model who appears in magazine covers of later episodes who looks basically identical to Satsuki, Natsumi's tomboy friend, but with blond hair and blue eyes.
Panty Shot: Happens to many of the females frequently in the manga. And not all that rarely in the anime...
Paper-Thin Disguise: Keroro's various "Pekoponian Suits", which range from sumo to businessman to schoolchild. These are robotic human suits with no head — the various characters riding them have their heads replacing the normal suit. So you have a 6 foot tall schoolchild with a giant frog's head. Note that these disguises always work perfectly. It's occasionally mentioned people take them for weirdos with masks, though.
On the flipside, headbands with googlibobs are all that's needed for humans like Fuyuki and Natsumi to walk unnoticed among the alien community.
There's a really odd example in the Girls' Day episode, where Kululu's Kululuko disguise is very good (i.e., looks just like a real human woman), but his identity is still very obvious to the viewer if not the cast (the name, the spiral motif, the color yellow, the voice, etc.)
Ironically, Natsumi still benefitted since nobody but her could see Keroro, and struggling to beat him allowed her to beat everyone else.
In the dub at least it was not so plot induced as it was youthful pride and not thinking induced, and to her credit it does hit her pretty fast just how bad an idea it was.
Portal Network: used extensively by Poyon (though the effectiveness is significantly reduced with the amount of time she takes to come out of it). The third movie involves Dark Keroro assembling his doomsday device, from massive pieces built all over the world, with equally massive portals.
Tamama also constantly uses portals to move around in the manga, an element that's only brought into the anime in the last season.
Public Domain Character: Grays type aliens, Flatwood monsters and eventually Chupacabras all appear through the series.
Queer People Are Funny- Watching a TV show in S 1 E 7. It is a parody of several anime. When the hero "explodes with the power of love" to save his girlfried, Keroro remarks offside "Interesting how his love for his GIRLFRIEND causes him to explode in a flaming rainbow..."
Red Eyes, Take Warning: Several cases. Assassin Captain Jirara has three. Dark Keroro's red eyes turn black when he is rid of Kiruru's influence.
Redubbing: A few years before the Sgt. Frog anime finally made it to North America, it was dubbed into English by Sony's anime-themed satellite channel Animax, giving it the title Sergeant Keroro. Although the acting (decent for Animax) may not have been quite up to American standards, this dub was considerably more faithful to the Japanese script than Funimation's dub. As a result, there are a few script purists who prefer it. A few clips of the Animax dub can be found online, for those curious enough to sample it.
Retcon: A fairly inoffensive one though. The official databook for the manga released alongside volume 23 changed the ages of several characters compared to their initial ones in previous databooks. Natsumi and Koyuki are 14 years old in the present, but now were 13 in the beginning of the series and Mutsumi now is said to be 16 years old (which would make him 15 in the beginning of the series), rather than 18 like in the previous official publications. In general, the new official ages seem to match up with the ones used by the anime, although Saburo still is one year older than his anime self.
In the English dub, the narrator makes notice of the show recycling the 'multiple of one character' gag, and gets tired of it.
Narrator "Last episode had two Momokas, now there's two Angol Mois? If we get two Keroros, I quit!"
Later in episode 23, Where there actually ARE more than one Keroro, he keeps his word.
School Clubs Are Serious Business: Fuyuki starts the paranormal club, but only has one other member in it (and she only joined because she had a crush on Fuyuki). The school newspaper also discovers the aliens' existence, but nobody believes them because they're a school newspaper (and because Fuyuki managed to confiscate their evidence).
Schoolgirl Lesbians: It seems like virtually all of Natsumi's class or teammates in the manga would die happy as the filling of a Natsumi/Aki sandwich. Except for Koyuki, who's only in love with Natsumi.
Later seasons and chapters seem to basically eliminate this side of her character, especially in the anime, although Koyuki remains one in the manga.
School Idol: Natsumi in the earlier seasons and manga volumes. However, this aspect of her character seems to be dropped in later chapters and episodes of the series, with later school scenes showing her more like an average girl.
Later seasons and chapters basically eliminated this side of her character. Natsumi's still popular in her class, but isn't portrayed as an idol admired by every girl in school anymore.
Sea Monster: One episode has several sea creatures crawl out of the ingredients pot and come in contact with the Flash Spoon, which turns them into giant sea creatures.
Second Place Is for Winners: The first beach comedy contest. Keroro enters to get a Gundam knockoff (because it's really rare due to poor sales). He doesn't find out that it's a consolation prize for everyone who doesn't til near the end...and he can't stop himself.
Serious Business: In episode 10, Keroro gets a cavity. The other platoon members notice this and immediately go all DEFCON 1, locking down the entire house, complete with steel barriers on the windows and doors, red rotating lights, and a loud klaxon. This is because cavities are actually caused by other alien invaders! Granted, these invaders are the size of bacteria, and so, are often confused with bacteria by humans.
More than once: in the episode that introduces Kogoro, he and the frogs disappear into another dimension in the middle of a pastiche of Kamen Rider, and when Natsumi asks "What the heck was that?", Fuyuki replies, "I think it was a parody of some old kids' show."
The size-changing Flash Spoon is a shout out to an episode of the Ultraman series where the protagonist attempted to transform into the giant hero with a spoon rather than the Beta Capsule. Its name is a shootout to a Doraemon flashlight with the same function. In the dub, it's called SpoonWOW and Sarge mistakes it for a dinglehopper.
There's actually a very similar line in the original, when Fuyuki asks Keroro to make it rain and ruin the sports festival, he receives a similar reply. Later, it's a desperate Keroro who receives that answer while bothering Kururu.
When empowered by extreme humidity in episode 4b, Keroro puts on a yellow shirt just so he can tear it off a la Hulk Hogan.
The best known example would be the depictions of Keroro's GunPla collection, down to individual versions. Some of the Keroro toys manufactured can even be connected to Gundam toys.
One episode shows Momoka hammering a table that Tamama is standing on, catapulting him into the air — the action freezes for a second as labels appear to indicate force applied, fulcrum, and work produced for an impromptu physics lesson.
When a Transformation Ray turns some koalas into humans, one of them says, "Mummy told me I must never leave this tree, or I'll die." Eucalyptus leaves really are the only form of sustenance for koalas, so there's some truth behind this.
Crosses into Product Placement in the fourth movie, with Shion's Citroen-looking limo and Aki's 2CV.
How many of us have even heard of the Anomalocaris before this show?
Played straight (Keroro's 'K66' and Kululu's '966') and parodied (one episode has shutter doors emblazoned with a NERVKERO logo)
The first OP uses this to represent their invasion.
Similar Squad: When digging for a spa, Keroro finds a superweapon left by a team of invaders not unlike his own. The dub takes this further, making them lizardmen from the planet Lizardono come to invade the planet they know as Ponopek but saddled with an incompetant leader who spends all his time building models. They even have similar insignias.
The first movie reveals that the ancient invaders who used those statues were actually Keronians, and they also left other weapons on Earth...
Sixth Ranger: Dororo in the manga could be considered this, because he only joins after the initial 4 man team (+Mois) was consolitated throughout several volumes of the manga. In the very beginning though, it was shown that the platoon had 5 members, so his status is debatable.
In the anime, Joriri joins the Keroro Platoon officially during an episode of the 6th season. However, because Status Quo Is God, it turns out there was a mistake and he leaves... That event was still referenced afterwards though and he continued to be a minor recurring character for the anime.
The manga introduced an actual sixth ranger in chapter 174. The "Second Keroro Platoon", a young recruit also named "Keroro", whose Keron Star gives him alternate modes based on the data of each platoon member. He befriends a human child called Tomosu, who's an occult fan and member of an occult club, similar to Fuyuki, but he's younger and actually a Fuyuki fan himself.
Slasher Smile: parodied when Keroro finally learns of Natsumi's one weakness...
SpaceX: there are dozens upon dozens of "Space" versions for festivals, TV shows, celebrities, anything you can name. The third movie ends with Dark Keroro attempting to invade another planet, only to be thwarted by Space Fuyuki and Space Natsumi.
Somewhere around volume 11 or 12 of the English edition of the manga, Tokyopop switched from using "Kururu" to "Kululu". This could have been due to a switch in translators, or the Japanese finally decided to settle some R/L confusion and told them how to transliterate it (they do that sometimes).
Angol Mois' name is was spelled "Moa" almost exclusively on this page... despite the fact that in her debut episode her name is spelled out in English as "Angol Mois".
Really a problem with transliteration. Her name is a pun off of the Nostradamus prophecy called "angolmois", but since Japanese phonetics are much simpler than French ones, it was simplified into "Moa".
It's worth pointing out that Tokyopop got this one wrong too, they still spell it "Moa", making this something of a case of poor research on their part.
Spikes of Villainy: Shurara's helmet is not only excessively spiky, but also has axe blades on it. And Momoka's Fawcett curls turn into spikes when she goes into psycho mode.
Stable Time Loop: sometimes invoked during the rare few time-travel episodes. The final Kero Zero chapter has our heroes responsible for putting their first human friend Kiko into space in the first place.
Lampshaded in one episode where Momoka visualises herself still watching Fuyuki quietly from a corner. In the future. Where both are well into their eighties. Apparently the Japanese are known to age well, but still...
Occasionally Subverted in the character development, even if they're Not Allowedto Grow Up. Natsumi evolves from someone who hates the Keronians into a fairly good friend of Giroro, while Keroro goes from someone who merely stops caring about his mission to conquer Earth in favor of being a parasite on the Hinatas, to someone who actually cares about them.
Stalker with a Crush: Momoka. She has her bodyguards spy on Fuyuki to find out what kind of underpants he wears. And that's only a minute fraction of the stuff she's done.
Better(?), Chiruyo Tsukigami, seeing as how she spies on Fuyuki personally, snapping pictures on her camera phone and scribbling in her notebook to boot.
Stepford Smiler: Kogoro, who never stops smiling. He's far less dangerous than the usual example though.
Lavie/Rabbie is the only one who can read his emotions.
Strange Pond Woman: In one story Tamama pretends to be a god (angel in the Funimation English dub) after being caught by a boy practising soccer. While he did help the boy become more confident he gave some rather strange advice, especially in the Manga and English dub not to mention teaching the boy a soccer kick fueled by resentment.
There's also the on-off character Tiger-Horse, a bizarre creature with some features of both animals but predominantly resembles a stringy haired ghost. To elaborate: Tiger Horse in Japanese is Tora Uma, referring to 'trauma' and its origins in Dororo's subconscious.
Tempting Fate: In episode 16, the narrator threatens to quit if there's another Split Personality story. Seven episodes later, Keroro clones himself and he makes good on his word until the end of the episode.
Theme Naming: Fuyuki, Natsumi, and Aki — whose names contain the words for winter, summer, and autumn respectively. Fan speculation that their Disappeared Dad will have the name Haru, for spring, is not unwarranted.
Also, many characters have names that can be and are converted to numbers, such as Mutsumi (623), Natsumi (723), Kululu (966), and many others. Helped by the fact that there are several different ways (old fashioned ways, modern ways, ways to avoid saying death...) to say the numbers, and that similar sounds (K sounds about the same as G, for example) can be used to keep character's names in this convention even if a syllable doesn't match up exactly with that of a number. However, three of the main five frogs don't exactly follow it (Keroro->K66, Giroro->G66, Dororo->D66, though as Zeroro, he may have been 066) and Tamama doesn't fit into it at all.
On the subject of the platoon, most if not all of the Keronians have a three syllable name with the second syllable being the same as the third.
Theme Tune Cameo: While doing chores around the house, Keroro sometimes sings his own version of the show's closing theme.
Another episode had Sumomo singing a few bars of the show's theme.
Another one had the first ending as Fuyuki's ringtone.
Played for laughs in the Kero Zero prequel story - it seems that "human abductions" are a well-known urban myth on alien civilisations like Keron, to the extent that the word "probing" has become a Freakout Button of sorts for our heroes.
Tamama, is always eating snacks, but not any specific kind. Candy, potato chips, anything. He's also fond of Space Okonomiyaki FX/Meat Lover's Space Omelet, but this very seldom appears due to being something of a delicacy... not to mention one that is still alive.
Turtle Power: One episode has Tamama coming across a tortoise in the countryside, plodding along the same path day after day. It's revealed later on that Fuyuki had that tortoise as a pet but lost it several years ago, and it's done nothing but make its way back to its breeder ever since. It succeeds.
Tyrant Takes the Helm: Tamama travels this path after a badly worded letter from High Command awards him with Keroro's position.
The Unreveal: The most noteworthy is the season 6 episode explaining Giroro's scar. It turns out the explanation given was a fake one devised for an infomercial.
And a season 7 episode about Dororo's mask in the end we don't see his mouth but the characters do, from their reaction it can't be that strange looking.
Actually, they're distracted by Keroro spilling some water or something and don't get to see it before Dororo puts his mask back on. It's probably nothing unusual though, since Dororo agrees to show them in the first place. (He does blush and... giggle... afterwards, but wearing a mask all the time probably makes taking it off feel like getting naked.)
Unwanted Harem: To date, Fuyuki has drawn the attention and affection of Momoka, Chiruyo, Alisa Southerncross, and the unnamed mermaid of the undersea Nontolma civilisation.
Don't forget Keroro's which includes Tamama, Mois, Pururu and in one episode Karara (in that episode they're all seen together, it doesn't go very well). It's also possibly included a girl who likes gunpla and Sumomo (only in the manga)
In the manga, there's also a female manga club member (who, although seemingly unnamed, was a minor recurring character) and Haruyo, a girl who befriended Sumomo.
Wholesome Crossdresser: All five Keronians have crossdressed at least once, with Keroro himself as the biggest repeat offender. On the flipside, Kululu's debut episode has him turning Aki back into a 14-year-old — whereupon she dresses up in Fuyuki's school uniform and sneaks off to his school. Their resemblance is uncanny.
Why Can't I Hate You?: Tamama views Angol Mois as his greatest competition for Keroro's affections, but sometimes has trouble viewing her as an enemy because she's too damn nice about everything.
You Would Make a Great Model: Tamama tries to discredit Angol Mois by posing as a sleazy camera man (with the help of a robotic exoskeleton) and telling her that she can become more "mature" by doing a photo shoot.