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: Dragon Ball
Badass Decay: While many of these characters don't complete their Badass Decay until DBZ, they do have a noticeable decline in effectiveness in this series:
Master Roshi: At the start of the series, he is stronger than Goku. He even beats Goku during the 21st World Martial Arts Tournament. By the Piccolo Jr. Saga, he is Demoted to Extra, and he stays that way through Z.
These days, Yamcha's mostly known for getting his ass kicked a lot. Most people forget that when he was first introduced in the series, he actually almost defeated Goku in battle. The only thing preventing him from the finishing blow so was that Bulma happened to wake up at that time, and Yamcha left because of his crippling fear of pretty girls. He was also the first person to use a KI technique and ended up saving everyone from Goku's Great Ape form at the end of the story arc.
Big Lipped Alligator Moment: The Penguin Village episodes. The segment is actually a crossover with one of Toriyama's other works, Dr. Slump, but to fans who don't get the reference it comes off as simply bizarre.
Broken Base: Dragon Ball vs. Dragon Ball Z is a not as commonly debated over but it happens.
The announcer for the World Martial Arts Tournament, so much so that when he didn't appear in the Cell Games saga some fans got quite irate. Fortunately, he makes his return in the Buu Saga.
General Blue, for being pretty much the only competent member of the Red Ribbon Army - starting at the point where he strangles an electric eel to death while it's still electrocuting him.
Akkuman/Devilman for having what could be considered the most powerful attack in all of Dragon Ball/Z. Hell he was even a playable character in Budokai Tenkaichi 3 (where he even gets his own what-if story), Dragon Ball: Advanced Adventure and Dragon Ball: The Revenge of King Piccolo.
Freud Was Right: As a child, Goku thinks girls don't have tails and guys do. Then he sees Bulma naked and thinks she's been castrated.
Germans Love David Hasselhoff: Special mention to Europe (specially France, Spain and Italy) and Latin America, where Dragon Ball is not only probably THE most popular anime in history, but also a full-blown pop culture classic. The fact that it became popular in those territories way earlier than in the US, definitely helped.note Although the anime was released in the US in 1989 (around the same time as Europe and Latin America) it took a whole decade and several re-releases for it to really catch up in the early 2000s. By that time, in Europe and Latin America Dragon Ball had been a massive juggernaut for years.
Harsher in Hindsight: Given what Dr. Gero did to avenge the fall of the Red Ribbon Army it makes Commander Red's real goal even more disturbing.
Commander Red is voiced by Kenji Utsumi in the Japanese version, and desires to become taller. Utsumi later voices a Stalinist rogue GRU Colonel, yet later ends up defeated by someone who looks a heck of a lot like a tall version of Commander Red in Metal Gear Solid 3.
The scene where Pilaf blows a kiss to Bulma in the Pilaf Saga becomes hilarious when his Japanese voice actor, Shigeru Chiba, ends up voicing another silly villain who has a huge amount of Foe Yay/somewhat Yandere-esque traits towards his nemesis. Bonus points for the fact that the villain's nemesis, Terra Branford, has an alternate costume that gives her a slightly similar appearance to Bulma.note In case anyone's curious, the alternate costume was based on her field sprite in her original game.
In the second episode of the anime, Bulma has this prophetic line:
"I don't know what planet [Goku's] from, but it's not Earth."
Magnificent Bastard: Demon King Piccolo qualifies, considering that he knew that Shen Long would have been called again with another potential reunion of the Dragon Balls (so he kills him before having any chance to depart).
Moral Event Horizon: The Pilaf gang freeing Demon King Piccolo from the rice cooker he was imprisoned in. Before that they had never done anything especially bad (except try to kill Goku and friends and they were laughably incompetent at doing so anyway).
Recycled Script: The Dragon Ball movies are all very loose adaptations of story arcs from the original manga and TV series.
Curse of the Blood Rubies adapts the first Dragon Ball hunt, with the original character King Gurume substituting Emperor Pilaf as the ultimate antagonist.
Sleeping Princess in Devil's Castle starts off with a sub-plot involving Goku and Krillin being sent to find the titular Princess (eventually revealed to be a precious diamond) for Master Roshi, just like when they were sent to find a cute girl for Roshi in the manga.
Mystical Adventure combines the Red Ribbon Army and 22nd Tenkaichi Budokai arcs and puts them in an entirely different context.
The Lord Slug movie matches the plot of the King Piccolo arc. An evil Namekian wishes for his youth and power. This one is painfully obvious.
And the tenth anniversary movie Path to Power retells the first arc of the first search of the Dragon Balls, but with the Red Ribbon Army as the main antagonists.
In the case of Mr. Popo, it doesn't help that when Bulma first meets him she blurts out "Doesn't he look a little dangerous?" Of course, in the manga Bulma then claimed that Mr. Popo was going to take her to a remote setting so that people can't see what he does to her. Officer Black, despite the design, fares better, as he's portrayed as actually far more competant than his boss, Commander Red. It helps even less that, in the manga and in the Japanese version, Mr Popo's speech is rather primitive, with Mr Popo referring to himself constantly in the third person.
Officer Black was "corrected" in The Path to Power, giving him a lighter complexion without differentiated lips. In fact, he looks more Hispanic than Black. Also in the Red Ribbon Army is General Blue, a Camp Gay villain with pedophilic implications and a deep fear of even seeing a woman.