5-Almost every storyline in Dragon Ball boils down to waiting for Goku to get in the fight and beat up the big bad, but it's easy to forget that the series' main protagonist rarely murders his enemies. Goku let Frieza slice his own goofy ass in half (while Future Trunks finished off Frieza in his Cyborg form), and Cell hit his own self-destruct button. The fact remains that, throughout Dragon Ball Z, Goku only kills two people. 

Both events occur during the Majin Buu arc. The first was Yakon, a low-level miniboss whose gimmick was devouring energy. All Goku had to do was overload him, like flexing to pop the bloody bowels of a pesky mosquito.
4-It's well-known within anime circles that Dragon Ball is loosely based on the centuries-old tale Journey to the West, in which a monkey boy flies on a magic cloud while wielding a size-changing staff. But the titular spheres themselves are actually inspired by an old novel series. Nanso Satomi Hakkenden, roughly translated as The Eight Dog Chronicles, was written way back in the early 1800s. 

In the original story, there are eight crystal balls, which were created when a Princess has sex with her father's dog. Don't worry, someone made an anime about it so you can see what that looks like. 
After being "born" -- again, from the unholy union of a woman and a dog -- the crystal balls went into the sky and split off, and later became human children. The phrase "Dammit, Japan" has never been more applicable.

When asked why there are seven instead of eight Dragon Balls, creator Akira Toriyama explained that he didn't want to have the same number as the famous story where a dog has sex with a human female who later gives birth to jewelry. Go figure.
3-There wouldn't be a Dragon Ball without Akira Toriyama, and as such fans owe him a lot of respect. However, like many mega-popular franchises, there comes a point where the collective fandom is more knowledgable and enthusiastic than the singular creator. When Toriyama cranked out 500 chapters of the manga, it was technically his job; whereas fans are free to watch and rewatch the material over and over again, it might be a little more trying for the guy who spent his career with these characters and their story. You can forgive the guy for spacing the little details, but Toriyama's forgetfulness goes beyond the pale. 

For instance, there's the fact that Toriyama forgot that there was a Super Saiyan 2 form. In his mind, it jumped straight from 1 to 3.
It's hard to believe that such a pivotal moment in the series could have possibly slipped by the dude who was responsible for bringing it to life. Toriyama says "I've really forgotten stuff..." as though he just realized he didn't get milk at the grocery store . This is more along the lines of forgetting to pick up your child at a soccer game, and then going on with your life as though the kid never existed.

It's gotten worse, probably because he's been more or less off the job in the two decades since Dragon Ball Z ended. When it came time for him to draw up some promotional art for his comeback movie Battle of the Gods, Toriyama drew Android 18 with purple hair. 
You might pass it off as a character choice -- there's nothing stopping Androids from dying their hair -- but since 18 showed up in BotG as a blonde, we can probably assume a very awkward conversation occurred between Toriyama and the production team.  

As unfortunate as that is, at least 18 doesn't have it as bad as poor Launch.
Don't remember Launch? That's okay, Toriyama doesn't remember Launch either. She was a major character in Dragon Ball prior to Raditz's arrival, and she even had a cool hook; whenever she sneezed, Launch drastically changed personality (and hairstyle). When DBZ rolled around, Launch snuck into a few scenes, but eventually disappeared for over 150 episodes. On numerous occasions, Toriyama has responded to inquiries about Launch with "I forgot."

Maybe we could learn something from Toriyama's bold memory-based approach to storytelling. Maybe if we all forget hard enough, Dragon Ball GT will never have existed.
2-If you're a native English speaker, it's easy to pass off a lot of the names in the series as just Japanese names. For all you know, there are guys named Nappa and Raditz all over Japan. But in almost every case, these names are actually puns. Super lame, adorable puns. 

As you might guess from the above image, almost all the Saiyans are named after vegetables. Goku's "real" name is Kakarot, which is a carrot; Vegeta is short for vegetable; Raditz is a radish, and so on. Most of the rest of the Z fighters are named after food. House of Infographics made a super handy chart of all the names The most notable character excluded from the pun trope is Mr. Popo, who was so named because Toriyama "thought it sounded comfortable." The unyielding void of Mr. Popo's soul-stripping stare is the last thing I'd call "comfortable," but to each their own.

What that chart doesn't include are the new characters that have appeared in the last couple Dragon Ball movies, along with the new anime series Dragon Ball Super. 
From left to right we've got Whis, Beerus and Champa -- all named after alcoholic beverages. Whis is whiskey, Beerus is beer and Champa is champagne. There are more characters in this pantheon yet to be revealed, so we could be looking at the introduction of Vodkadon, Bourbo or Saken. Really, anything but Appletinius will do.
1-As popular as DBZ is in the Western world, it's even bigger in its home country. Japan goes nuts for DBZ, especially since the franchise has seen a resurgence in the last few years. It's gotten to the point that Japan recently elected to spend money to support Dragon Ball by awarding a grant for the movie that arguably ignited DBZ's comeback: Battle of the Gods.

Japan's Co-production Certification Program funded production to the tune of 50 million yen, or about $600,000. That might not sound like a lot in movie terms, but this isn't Hollywood. The Frieza-focused movie sequel Ressurection F cost five million dollars to produce, and BotG very likely cost less. Which means that you have the Japanese government to thank for at least 1/10th of that movie. We'll just assume that 10% had nothing to do with Vegeta singing and dancing.