Dragon Ball/Filler/Headscratchers

Red Ribbon Army/Mercenary Tao/General Blue Saga filler

 * When the young Goku was getting visions from Corin's three water vessels, the past and present visions made perfect sense. The future vision, on the other hand, was mainly about Dragon Balls knocked around like billiards, and Goku getting attacked by giant centipedes. This isn't ringing any bells.
 * This was anime-only, right? They were probably setting up for some filler that never materialized.
 * Or they were just being vague because they didn't know what was going to happen later in the anime.

King Piccolo Saga filler

 * Did Kami Sama actually send young Goku back in time to Mutaito's school and all those other places, or was it imaginary? (There were several hints that it was real, but... why?)
 * It was all anime filler, so I have no idea

Saiyan Saga filler

 * In the anime, why were Nappa and Vegeta coloured differently before arriving at Earth?
 * Probably because they were in space. The bug planet they landed on along the way had a different atmosphere and... um... maybe the colour of the sun was different...? I'm not too sure, but that would be my best guess.
 * Continuity fuck-up. They only decided on their final canon anime color after their brief appearance in that planet. In-universe, you are supposed to pretend they always looked the way they do now, just like when a Soap Opera gets a replacement actress no changes to the character's physical traits are meant to have actually happened.
 * The actual reason is due to Toei having to choose the color pallet themselves, simply because at that time neither Vegeta nor Nappa had been seen colored in the manga, their next appearance had their colors "fixed" Also of note is in Dragon Ball Kai, Toei went back and colored Vegeta's hair the correct color in that scene, though they left Nappa's armor color alone, so one can simply assume that between his first and second appearance he simply changed into a different colored suit of armor.


 * When Goku was wished back after his first training with King Kai, in order to fight the saiyans, why did he waste so much time running down Snake Way again, when he could've just jumped off it into HFIL and taken that shortcut to King Yama's desk drawer again? He could've been back on Earth inside of an hour that way.
 * It's safe to say that HFIL is quite a huge place. Depending on where on snake way he drops, he might land in a different part and it might take exactly as long to get to the tunnel to Yama's desk. And once down there, how could he know where to go? HFIL isn't exactly full of friendly people. Anyway, there was no way Goku could be sure.
 * That was an anime bit of filler, in the original manga there is absolutely no way to get back if you fall into Hell and so he had to run down Snake Way.
 * Because he would still had to travel a long distance to get back to the shortcut, in fact the Snake Way isn't a complete straight line, so he would had taken even longer just by trying to figure out were to go.

Frieza Saga filler

 * When Goku's friends are training after they are killed, Kaio says that if they die now, nothing will happen, since they are already dead. Then Piccolo kills Chaotzu, and Chaotzu is fine. However, during the Buu saga, Goku says that if he dies while being already dead, he'll disappear. What?
 * It might be that a dead person killing another dead person has no effect while Buu, thanks to his dimension hopping powers, can kill with the whole existence erasure effect. That, or Retcon.
 * No, actually, it's because the whole thing is anime filler, and Toriyama hadn't made up his mind on that issue before Buu Saga. It's also possible that if you "die" in the Underworld you're okay, but if you come back to Earth and "die" somehow, you'll be erased.

Cell Saga filler

 * Okay, so Goku and Gohan are training in the Room of Spirit and Time and Gohan is trying to reach the level of Super Sayian by way of "pain from loss". When Goku says, "Imagine Cell killing us all." Gohan says he has no idea what Cell looks like. That's all fine and good...right when we get into Gohan's nightmare of Cell killing his mother and Piccolo. What bugs me? If Gohan didn't know what Cell looked like, then how was he able to picture Cell exactly how we know him? Did Goku describe/draw Cell for Gohan? Was this just for our conviences so we wouldn't be confused?
 * Most likely anime filler. I just read that part in the manga, and Gohan didn't imagine Cell killing anyone. Goku just says "Fine then, Freeza or whatever." Gohan tries a bit, fails, next time we see him he's gone Super Saiyan already.
 * Sayians do seem to have a degree of psychic powers, even in the manga (Goku reading Krillin's mind on Namek). I think this can explain how his subconcious was able to construct an image of Cell.


 * During the filler before the Cell Saga, Chichi has Goku learn to drive so he can take her shopping. Then who's driving the flying car when Chichi drops Gohan off at Master Roshi's house before they take off to go to Namek?
 * You said it best: filler. Also, it's not just for the shopping, it's so Goku does something and isn't a poster boy for the NEETs.
 * IIRC he's shown driving several times in the manga, so he probably got the license long before. The real question is why he and his family don't just fly. Maybe the neighbors will talk.
 * Can Chi Chi even use ki - much less fly? as far as I can tell she's the female Yajirobe.
 * Probably not, but if Videl can learn in a few days then so can Chichi.

Buu Saga filler

 * In Hell, why is Dr. Gero allowed to keep his Android 20 body? Frieza used to be a cyborg and his natural body was restored, but why not Gero's natural body?
 * A) Because it's filler
 * B) Maybe Gero just created his Android body to look EXACTLY the same as his Human body
 * Even the glass view of his brain?
 * I've always imagined that Gero, for some reason best known to him, re-converted himself in Hell.

Uncategorised

 * There is a particular Filler episode in the Anime where Chi Chi hires a Private Tutor for Gohan - who begins to continuously beat him. Was that sort of thing even remotely legal in Japan when the episode was first aired?
 * Well, I think the setting of Dragonball is an odd mesh of modern times and Feudal Japan. Perhaps, back in Feudal times, it was the norm for tutors to beat students that weren't acting right, I have no idea. I'm sure people in modern Japan would frown heavily at a private tutor who seriously thinks beating his/her charges is a good idea.