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.
A Gundam Wing parody in Episode 320 has Kururu turned into a Zechs Marquise-like character. Takehito Koyasu, Kururu's Japanese voice actor, also voiced Zechs in Gundam Wing.
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.
A competent officer who constantly has to put up with a frustratingly Wild Card that he can't control. Are we talking about Giroro and Keroro or Van and Asch? Hilariously, this one got lampshaded in the RPG where Giroro got to use Van's Ancient Requiem, as one of his specials.
It's not hard to imagine Geroro shouting "WAHOO!!"
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.
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.
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.
That said, 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
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 This one actually happened in most non-Asian countries to air Frog, so Funimation wasn't exactly pulling a 4Kids here, 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.