These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
YMMV: Sgt. Frog Abridged
Ass Pull: Most of the second half of Episode 10. ThornBrain (Under "CSD", his wiki alias) admitted that the team "were making it up as they went along". Because it was made up on the spot, the Episode 1-3 remakes that came shortly after made sure to foreshadow it.
They did attempt to link up several previously unrelated parts of the first season in the process, but almost none of it was "planned" until after the release of Episode 9, thus making it eligible for this trope. See the Chekhov's Gag entry for the main exceptions in the episode.
At some points, Giroro. Flashbacks makes him nauseous, and he is allergic to cats. Episode 17 also revealed that he never properly learned how to shoot a gun and never finished military training, evidenced by his failure to land a single shot on Garuru.
Invoked with Zoruru, and after only one scene. His first appearance has him kill Koyuki immediately following a Pre-Mortem One-Liner. His second appearance has him getting a disruptive Skype call from his mom, followed by excessive paranoia about how Natsumi must want to start dating him.
Dororo was this at the start of the series, even to the writers, (Yoshi didn't even want him in the series before his first appearance), and he was the one character who ultimately developed the most. When the series finally ended, he was voted Travis, Yoshi and Thorn's favourite character.
Tororo got a massive wave of praise after Episode 17. It could have been because Tororo has a large fanbase already, or simply because Travis did that good a job.
Practically every non-recurring character became one, including Asami, Grandpa Viper, the animators, Joriri, Pururu, and the "teeth guys". Yoshi often lamented that these characters did not show up more often, since he loved how they ultimately came out.
Hilarious in Hindsight: The writers made all of the characters defaulted to bisexual unless stated otherwise, and Giroro was also made a Wholesome Crossdresser. Writer ThornBrain came out during production of Episode 11 as a bisexual transvestite, which he was only starting to realize around the time Giroro was made a crossdresser.
The series made Keroro and Tamama a couple. Subverted after Episode 10, when it is discovered that Tamama is actually a girl.
Giroro and Dororo. Dororo actually hit on Giroro at the end of Episode 6, they have a semi-serious bit of bonding at the end of Episode 7, and they are noticeably closer friends by Episode 11. Then in the Post-Credits to Episode 14, Dororo asks Giroro to marry him. And then They Do get married in Episode 15. Giroro even says "We've been fucking behind your backs for months!"
Growing the Beard: The creators consider Episode 4 to be the point where everything in terms of writing and voicing starts to gel, be it due to the expulsion of previous redundant team members or simply the introduction of Dororo. Yoshi also didn't really pick up as a voice-actor until Episode 4.
Nightmare Retardant: Intentionally in Episode 10. While the Nightmare Fuel level of Future Kululu's scene is debatable, the sudden appearance of R.E.M.'s "Shiny Happy People" video in the background is a signal to the viewer that things are going to get stupid.
Writer Thorn considers Episode 13 to be the series' low-point, and although the episodes after were fine, he thinks Episode 17 was when SFA finally dug back out of it and truly get its spark back. This was mainly due to him and Yoshi jumping ahead and planning for 17, and the resulting excitement for such a later episode left them with no ideas or motivation for 13; it took them three tries to find an episode they could work with, and the resulting script was dry and unimpressive. Yoshi and Travis generally agree that 13 was "kinda bad", whereas all three (and many viewers) agree that 17 was one of the series' best episodes.
Earlier, bringing Travis in to help write Episode 9 was Thorn attempting to prevent this trope after a particularly idea-less Episode 8. Episode 10 was also written with a back-to-basics approach after Thorn realized that Episodes 8 and 9's biggest flaw was that they were too self-aware.
Tear Jerker: Fuyuki's speech to a brainwashed Keroro in the finale:
Fuyuki: "You're right, Keroro. It is funny. Somehow you managed to turn everything that happened into everyone else's fault. You ever think about why you can't make people happy? Because nothing you've done in your entire life has been for anyone else. You hurt my sister for questioning you, you abandon Tamama for being herself, you take advantage of Giroro for keeping the team together, you mock Dororo for his undying devotion to you... and tell me, Keroro... Did you ever once think of what I go through to protect you!? (Crying) You donít care about anyone... You just drag everyone through the dirt... Now everyone who ever cared about you hates you... But it didnít matter to me. You were my friend, the only real friend I ever had. I took everything you gave us... ícause I wanted you to be happy. Does that mean a fucking thing to you?!"
This actually came about as a result of Writer Gender Confusion: for the first several months of the team's existence, Thorn kept thinking Tamama was a girl. By Episode 3, he and Yoshi just decided to make it that way.