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: Ben 10
And the Fandom Rejoiced: Cartoon Network has announced a new TV-Movie based on this installment of the franchise will air in 2012. Though some may be wary of Destroy All Aliens being CGI animation instead of traditional, the movie certainly wins points for bringing back the original cast to reprise their respective roles and being written by one of the writers from the original series, Marty Isenberg.
Complete Monster: Dear god, this series has a total of three, all of which are pretty much the seasonal Big Bads.
Vilgax, a villain who destroyed Tetrax's homeworld, was about to cut Ben's arm off just to get the Omnitrix off (in "Gwen 10", when Gwen asked if they couldn't just slip the watch off, Vilgax responds "And what fun would that be?", and indeed, there is a much easier way.). Among other horrendous deeds.
Kevin 11, who was going to wreck a train full of innocents to get money, permanently scarred an officer of the law and framed Ben, threw every chance at redemption Ben offered him away, has gone on to make it clear he wants to outright murder Ben (as well as those close to him) and once almost attempted to via impaling him with a diamond shard. And as an adult in the future, tries to murder Ben's SON, and actually uses his OWN son to do so, then telling his son outright that revenge on Ben is more important to him than he is.
Now, if one is going by his new characterization by the new creative team in the Ben 10 Alien Force, then he is removed from this trope. But if one is just going by how he was portrayed by the original creators, he certainly belongs in it.
Ghostfreak. The type of guy who will possess a young girl and threaten to make her jump off a roof to her death if her cousin doesn't comply with his wishes. Or cover the world in darkness, which causes everyone on the planet to horrifically mutate.
Zombozo, a zombie vampire clown who consumes laughter (draining them of positive energy, apparently), this doesn't sound so bad, but then he kidnaps Gwen draining her until she's pretty much almost a withered husk, and given that he's so casual about it, he's probably done it before, and if you think of it a few other ways, there's a very frightening subtext in there. Incidentally, he was killed by the abovementioned Ghostfreak.
Ensemble Darkhorse: Lucky Girl, who is ironically one of the leads in disguise. Her nemesis Charmcaster qualifies on the villain side of things.
Naturally, some of Ben's aliens are more popular than others, but the one who takes the cake (from the original series, at least) is Heatblast. He's enough of a dark horse than a Ultimate Alien DVD was titled the Return of Heatblast.
XLR8 is also pretty popular, which makes it extra baffling that they went and made Fasttrack.
Fridge Logic: So, if Ben was so desperate to unlock the secrets of the Omnitrix, why didn't he just use Grey Matter's intelligence to do so? Amusingly, Kenny in "Ken 10" does think to do this.
Germans Love David Hasselhoff: Gwen is apparently popular enough in Southeast Asia that Cartoon Network Asia gave her a website and a good amount of merchandise.
The Franchise is also very popular in Denmark, where many stores hold entire sections of Ben 10 merchandise.
Remember that ending in Gwen 10 where the Omnitrix ultimately ended up on Grandpa Max? Several episodes later, some alien named Xylene, a person from Max's past, revealed that the Omnitrix was originally for Max. But thanks to the fact that Ben's DNA was close to his, and Ben was the one who discovered it, it ended up on him.
In the end of "Kevin 11", Ben offers Kevin to join him and become allies. Soundfamiliar?
I Knew It: Some guessed that Ghostfreak would turn evil when they found out the Monster of the Week was an Ectonurite in "Ghostfreaked Out", despite some sources saying that it was a completely separate Ectonurite. When the episode aired, the truth became apparent after a nightmare detailing Ghostfreak telling Ben to let him out of the watch, and then subsequently escaping the watch after dealing with Zombozo's unemployed henchmen.
Just Here for Godzilla: Some people just watched the show to see Grandpa Max be completely awesome.
Moral Event Horizon: Kevin was going to crash two trains together, one full of cash, the other full of innocent lives. Most of the other antagonists before this were more formulaic in their general supervillainy, but this? That's going too far.
That's nothing. As an adult in the future, he wanted to kill Ben's ten-year old son just to get at Ben...and manipulated and then pushed aside HIS own son Devlin in order to do it, flat-out saying he cares more about revenge on Ben than about Devlin.
Vilgax destroys the planet where all of Tetrax's race lives, killing hundreds of innocent lives for no reason other than to test his brand new toy.
And Ghostfreak wanted to plunge Earth into darkness, the result of which is shown to be horrifying mutations of all living things.
Also note, that was just a side effect of his plan that he didn't even care about.
Zombozo gets his by kidnapping a 10 year old girl and draining her of her energy until she's nothing but a shrivaled husk of her former self, speaking of it so lightly that it's implied it's not the first time.
Older Than They Think: There really was a secret organization called the Plumbers - Richard Nixon's private police who did the illegal surveillance of the Watergate hotel.
Relationship Writing Fumble: Ben and Gwen, in an almost reverse case of the usual trope. The writers PROBABLY viewed them as just bickering, if still loving, cousins (and nothing else), and tried to write them as such. To most of the rest of us...
This actually created a Periphery Demographic all by itself. Older viewers initially hated the show, partially because of the flat, immature, two dimensional characters. The instant they decided Ben and Gwen had crushes on each other, the characters gained two or three levels of depth, skyrocketing it to the top of a lot of teen's lists.
Seasonal Rot: The third season is generally considered the weakest due to less impressive episodes and overall story arc than the other seasons have.
They Changed It, Now It Sucks: Race Against Time. Dear lordy, Race Against Time. Loyal fans were NOT happy when they realized the aliens were not voiced by the original voice actors.
Visual Effects of Awesome: "Destroy All Aliens" has particularly impressive CGI effects, with the Galvanic Mechamorph's fluidity being especially noticeable.
