* AccidentalInnuendo: The show has Kevin uttering the line "I don't know if I can pound your Grandma!" He means he's unsure he can fight her... but ''still''.
* AlternateCharacterInterpretation:
** Gwen's and Kevin's crushes on each other are just their way of repressing that they're both attracted to Ben. Both attractions are at least partially taboo -- Gwen's because [[KissingCousins Ben's her cousin]], Kevin's because [[HoYay Ben's a guy]] -- so the only solution is to try to force themselves to fall (however [[StrangledBytheRedString improperly]]) for each other. Because they're both lying to themselves and each other, they're both getting their [[MasterOfTheMixedMessage signals returned]], which is encouraging the charade. This explains why Gwen tells Kevin to ask her out without wanting him to, why Kevin tries to make himself appear attracted to Gwen without making a move, and why they both show Ben so much more subtle and genuine affection.
** Is Vilgax a NobleDemon and a benevolent ruler on Vilgaxia who genuinely cares about his people, or just a [[PragmaticVillainy pragmatic villain]] [[VillainWithGoodPublicity who keeps a good image to get their support]]? Was he always like this, or did he change during the five years between this show and the Original Series?
* AngstWhatAngst: Despite Grandpa Max apparently dying in Season 1, Ben and Gwen's fathers don't seem to be in particular mourning over him. To be fair, they're only seen in one episode apiece, but one such episode ("What Are Little Girls Made Of") does reference what happened to Max quite a bit.
** Also, right after he seemed to die, Ben and Gwen ''immediately'' composed themselves. No tears, no anguish, no nothing.
* BadassDecay: Kevin and Vilgax suffer a lot of this. The general consensus is that Kevin got better in Season 3 (something that is even lampshaded in "Time Heals"), but Vilgax (ironically only featuring in that very season) never recaptured his former glory.
* BaseBreakers: The ten new aliens Ben gets at the beginning of the show started out as this, due to most of them having powers that were essentially combinations of previous forms. Some fans saw them as blatant and lazy rip-offs, other perceived it as a clever way to have Ben get new aliens while still retaining a set of powers they were familiar with, and believed the powers had been merged creatively enough to make them interesting. However, with time they have come to be accepted by the fandom (some like Big Chill even becoming {{Ensemble Darkhorse}}s), and those who still criticize them as rip-off now mostly consists of really hard-core Original Series fans.
* BrokenBase:
** The series as a whole started the split in the fanbase that would keep getting worse in the following sequels. While a lot of fans despised the show (see ContestedSequel above), some of them actually loved the DarkerAndEdgier take and found it an improvement for maturing the main characters (particularly [[TookALevelInBadass Ben]]).
** The retcon about Gwen inheriting her affinity with magic[=/=]mana-manipulation powers from her grandmother being an alien. Some saw it as a pointless retcon taking away diversity from the team (based on the idea aliens should be ''Ben'''s gimmick), other think it added more background to the character and reduced her CanonSue side by ''finally'' explaining why she was that good with magic. [[TakeAThirdOption Alternatively, other feel]] [[TheyWastedAPerfectlyGoodPlot the idea was good, but poorly executed due to making it unclear if Gwen's powers were really magic, fully aliens or both]].
** To a lesser extent, there is a similar split about Kevin being half-alien and [[spoiler:his father being a Plumber who was Kevin's partner]], though the reasons are slightly different than the one above. While the problem about Kevin being half-alien rather than mutant and removing the diversity remains, fans against this change are mostly complaining it contradicts both the franchise's chronology and Kevin's initial backstory. Those who support it feel it gives a bit more depht and motivations to the character. This would eventually lead to an equally controversial retcon in ''WesternAnimation/Ben10Omniverse''
** As a whole, Kevin's HeelFaceTurn; some fans felt he worked better as a villain, complain this took away one of Ben's coolest and most iconic [[ArchEnemy Arch-Enemies]], and feel the change in his personality was forced. Others like him as a protagonist for his snarky humor, and think it developped him from a generic AxeCrazy villain to a more interesting protagonist.
** While most fans agree about Vilgax suffering VillainDecay, there is some debate around the fact he is implied to be a benevolent ruler on his planet, and the scene of him [[PetTheDog rescuing a little girl from his species]] ([[LickedByTheDog who then hugs him]]). Some consider this gives him HiddenDepths and makes him potentially more interesting than a bland EvilOverlord, other see it as yet another instance of him being made less scary, and feels it seems out of character for a guy who once blew up a planet just to test his new weapon.
* CharacterRerailment: Vilgax's characterization and voice (though the voice was done by JohnDimaggio rather than by Creator/SteveBlum) were a bit closer to how he was originally portrayed in [[WesternAnimation/{{Ben10}} the first series]] in the video game ''Vilgax Attacks!''.
* CopyCatSue: Albedo is a possible [[ParodiedTrope parody]]. He got a second Omnitrix, helped create the original, comes back with even more powerful version of it and he got an [[PaletteSwap incredibly simple design]].
* ContestedSequel: Quite a few people treat ''Alien Force'' as this and thus FanonDiscontinuity, mostly because of stuff like [[TheyChangedItNowItSucks making Gwen's magic powers into alien energy manipulation]] and [[RetCon that a lot of things in]] ''[[RetCon Alien Force]]'' [[RetCon don't match up and even ignores stuff established in]] [[WesternAnimation/{{Ben 10}} the original series]]. Still, some fans ''did'' appreciate this sequel, as noted in BrokenBase above.
* CrazyAwesome: Rath practically ''runs'' on this trope.
* CreepyCute: Big Chill ould be considered this. While his Reaper-like mannerisms and monotone voice do tend to be rather disturbing to some, it is mostly offset by eerily beautiful color scheme of his wings and body, as well as an almost feminine slender appearance.
* CreepyAwesome: Darkstar was complete NightmareFuel in his first episodes, and it definitely played in his favor to make him popular.
** To a lesser extent, Big Chill.
** AxeCrazy Ben in "Above and Beyond". [[spoiler:It was all an act]], but it's amazing how Ben can make a surprisingly good villain.
* CriticalBacklash: While the show is by no mean flawless, it's definitely not as bad as [[TheyChangedItNowItSucks Original Series fans tend to describe it]]. The first two seasons, especially, are considered quite good of their own by a lot of fans.
* CrossingTheLineTwice: Jarret [[spoiler:[[EatsBabies eating the Tiffin]]]]? Not funny. ''[[TheCynic Kevin]]'' fainting after seeing this? Hilarious.
** In the same episode, Kevin implying that Argit not only actually sold his grandmother, but got a top price from her.
* CrowningMomentOfAwesome: Rath [[spoiler:diving into the giant [[WesternAnimation/TeenTitans Trigonesque]] alien to rescue the Tiffin and escaping by punching the guys teeth out from the inside and threatening to "knit [his] organs into a sweater" if he tries to retaliate.]]
* DamselScrappy: Julie is perceived like this by some fans, but it's mostly an undeserved reputation caused by WhatMeasureIsANonBadass; she actually got kidnapped only thrice over the course of ''five'' season, which is fairly low as far as Super-Heroes' {{Love Interest}}s go, and, by the time she got Ship, she was perfectly capable of defending herself of her own.
* DracoInLeatherPants: Albedo, though easily explainable due to his IneffectualSympatheticVillain status.
** Darkstar is an even bigger case, and unlike Albedo, he doesn't have ''any'' sort of redeeming features.
* [[GermansLoveDavidHasselhoff English Love Alien Force]]: While the show is seen as a ContestedSequel in USA, it generally was a much bigger hit than its predecessor in the United Kingdom.
* EnsembleDarkhorse: '''You like Rath, dontcha?''' '''[+Everyone likes Rath!+]''' '''[++[[BoldInflation You know what happens to people who don't like Rath]]? [[CatchPhrase LET ME TELL YOU SOMETHING]], GUYS WHO DON'T LIKE RATH!!!++]'''
** [[CreepyGood Big Chill]] also is fairly popular amongst fans for his cool design, similarities to Ghostfreak and good voice.
** Swampfire, who was Wildvine and Heatblast combined, with an [[ComboPlatterPowers arsenal of powers]] and impressive design was also well received.
** [[EvilTwin Albedo]], who rarely appears (he only had two appearances in this show and two more in ''Ultimate Alien''), is surprisingly popular among the fans too, as mentioned previously. In fact, he was so popular, ''WesternAnimation/Ben10Omniverse'' raised him to BigBad rank for an entire arc.
** And let's not forget time-travelling [[Series/DoctorWho the Doctor]] {{Expy}} Paradox, whose even most of the Alien Force haters actually ''love''.
** Darkstar, one of the [[KnightOfCerberus scariest villains in the series]] and an {{Expy}} of ComicBook/{{Raven}} and SelfDemonstrating/DoctorDoom.
** Fangirls and the furry fandom consider Argit as this.
** Reinrassic III; granted, he is an important character, but he only had three appearances in the whole show. Yet you would be surprised to see how many fanart there are of him.
* EvilIsCool: Not as many cases as the Original Series, but the show still gave some fairly memorable villains. [[KnightOfCerebus The Highbreed]], [[TheSociopath Darkstar]] and [[EvilTwin Albedo]] come in mind.
* EvilIsSexy: Still Charmcaster. Ben and Kevin even lampshade it in the episode she appears in.
-->'''Ben''': Was she cute?
-->'''Kevin''': More than cute; hot!
** Michael Mourningstar too, when he doesn't have his zombified face.
* FanPreferredCouple: If you haven't already noticed that there's a large fanbase who hates Kevin/Gwen and wants Ben/Gwen, this is probably the first time you've ever visited TV Tropes (though oddly, Ben/Julie isn't quite as reviled after Julie got RescuedFromTheScrappyHeap.)
** There are quite a few who want [[HoYay Kevin/Ben]] as well.
* FanficFuel: The whole Plumber's Kid is based around the idea that a lot of [[HalfHumanHybrid alien-human hybrids]] exist on Earth due to former Plumbers mating with humans. This makes for an excellent justification for fans to create their own half-alien Original Characters.
* FoeYay: Gwen with both Darkstar and Charmcaster. Ben and Kevin qualify as "Former Foe Yay".
* FranchiseOriginalSin: While the overall story arc was well-received, there were many Filler episodes often seen to the detriment of the story arc, some going at odds with the tone being established, but were able to be freely ignored if the viewer so pleased. These problems (too much Filler and goofy plots) have since become the biggest criticism of ''Ben 10 Omniverse'', where later arcs have so much Filler, the arcs are shorter and developments become abrupt due to it.
* FridgeHorror: Imagine being Alien X. You're [[PhysicalGod all-powerful]], [[RealityWarper capable of bending time and space]]... and unless [[LawfulStupid the voices in your head agree to do anything]], you're [[TakenForGranite stuck in place]], [[AndIMustScream forced to stand by]] while [[ApocalypseHow horrible things happen]].
* GeniusBonus: The Tiffin. If you know what the term means then it's no surprise that [[spoiler: he's going to be eaten.]]
* GrowingTheBeard: Season 1 didn't really have a clear story arc and included many fillers. Season 2 improved things a bit, continuing previous episodes, giving a slightly clearer progression, rescuing Julie from the Scrappy Heap and actually concluding to a real finale. Sadly, [[SeasonalRot season 3 didn't work that well]].
* HilariousInHindsight:
** You might have to squint to see it, but Professor Paradox's status as an Expy of The Doctor seems downright prophetic if you think he looks like a younger Peter Capaldi.
** Psyphon was created as an expy for Desaad. His voice actor, Creator/DeeBradleyBaker, voiced Desaad in ''WesternAnimation/YoungJustice''.
* LikeYouWouldReallyDoIt: Nearly averted with [[spoiler: Max]], whom they ''were'' planning on killing off, but decided not to.
* LoveItOrHateIt: The show is either loved for bringing a new more mature approach to the series and making Ben [[TookALevelInBadass significantly more badass than in the Original Series]], or hated for its difference with the Original Series and the poorly-written romance. Everybody, though, seems to agree about hating [[SeasonalRot Season 3]].
* {{Misblamed}}: When many of fans of the original Ben 10 complained about the questionable changes, they often blamed Creator/ManOfActionStudios for it. Despite the fact Man of Action has little to nothing to do with this show or any other beside the original except serving as executive producers.
* MemeticLoser: As noted in NeverLiveItDown, [[ArchEnemy Vilgax]] is constantly seen as a poor villain and a joke in this series due to the VillainDecay he suffered. While said decay is real, it's nowhere near the level fans tend to attribute him.
* MemeticMolester: Darkstar could almost rival [[WesternAnimation/TeenTitans Slade]] in this department. Really, you could make reasonable arguments that fanfics despicting him as a rapist are not ''that'' OutOfCharacter with him.
* MemeticMutation: "BRING ME CHILLI FRIIIIIIIIES!"
** Also, Rath's "Lemme tell yah something" catchphrase have become quite popular.
* {{Narm}}: Vilgax's so-called ultimate form? [[spoiler:A giant green octopus.]] Sad because it could have been a great scene if not for limited efforts on the design and a fight that is not even seen onscreen.
** Ragnarok pretty much loses all credibility when itís revealed the key he was looking for [[spoiler:goes in his ''forehead''.]]
* NeverLiveItDown: While Vilgax ''did'' suffer DiminishingVillainThreat in Alien Force, he still had his share of BadAss moments, including having a CurbStompBattle with all the Plumbers Helpers ''and Max'', defeating several of Ben's most powerful alien forms (Jetray, Big Chill, Humongousaur and Chromastone) one after the others, destroying a whole ship of his own to free Ghostfreak, having a decent fight with Ghostfreak (which [[spoiler:he won]]) and [[spoiler:actually getting the Omnitrix in the finale, which led to the show's DarkestHour]] . However, the only things most fans retain about his Alien Force incarnation are that he was following a Galactic Code (even through both the series and WordOfGod shew he did it only out of PragmaticVillainy) [[spoiler:and that he got defeated by Diamondhead, who couldn't even scratch him before]].
** While Julie did got RescuedFromTheScrappyHeap, a lot of Alien Force haters just aren't willing to accept her and still consider her a SatelliteLoveInterest.
* NightmareFuel: Ben turning evil in "Above and Beyond". [[spoiler: It was all a test put by Max in order to see if the kids could handle the Plummer Academy]], but it was still pretty unsettling to see Ben act like a complete psychopath as he toys with the recruits.
---> '''Manny''':I know you're in here. Come out and show yourself! The others might be afraid, but I'm not scared of you!
---> '''Ben''': That's because the others are ''smarter'' than you.
* PanderingToTheBase: Season 3 is this to fans of the original series who didn't care for the more mature direction that ''Alien Force'' went with in the first two seasons. This... [[SeasonalRot didn't work out quite well]].
* ParanoiaFuel: The [=DNA=]liens can use ID masks to disguise themselves as whoever they want in order to infiltrate and invade the humans right under their noses. They can literally be anyone, and ''Max Out'' reveals [[spoiler:they can turn humans into more of them]]. They can basically be anyone and anywhere.
* PortmanteauCoupleName: Gwevin (Kevin and Gwen), Benlie (Ben and Julie), Bevin (Ben and Kevin), Bwen (Ben and Gwen).
* RescuedFromTheScrappyHeap: General opinion is that this happened to Julie midway through season two, thanks to the show developping her bound with [[CoolPet Ship]].
* RomanticPlotTumor: Gwen and Kevin, quite often.
* TheScrappy: Julie was this for a while, but got RescuedFromTheScrappyHeap midway through the second season. Though some fans consider she fell back into this territory later (See the ''[[WesternAnimation/Ben10UltimateAlien Ultimate Alien]]'' YMMV page for more details)
** There are many who don't like the Anodite species as a whole, due to what is felt to be a pointless, as well as sometimes incredibly confusing Retcon, with the representatives of the species [[JerkAss not being]] [[BlueAndOrangeMorality very well-regarded either]].
** Humungousaur is very unpopular in the fanbase, due to Ben [[SpotlightStealingSquad overusing him]] in favor of the more popular aliens like Big Chill and Swampfire, while there are countless SuperStrength aliens who are more creative than him. Doesn't help that his ''one'' unique power ([[SizeShifting growing bigger]]) was seemingly forgotten starting with season 3.
* SeasonalRot: The third and final season seems to be the least popular overall. Fans of the first two Alien Force seasons mostly dislike it because it took a lighter tone, focused on filler episodes rather than having a story arc and started making Ben immature again, while Original Series fans mostly dislike it due to bringing back Original Series villains only to give them completely different designs and inflicting a major case of DiminishingVillainThreat to Vilgax. Not that it's ''entirely'' hated though, as it ''did'' introduce us to [[EnsembleDarkhorse RATH!!!]]
* StrangledByTheRedString: Gwen and Kevin -- The ship is dropped on the viewer with absolutely no set-up, no basis, no rationality ''in the very first episode''. Kevin almost wrecking his precious car to tell Ben not to be rude to Gwen could be attributed to his BadassDecay, but "I'll follow you anywhere"? Were the writers afraid that if they took the time for some actual development, the show might be canceled before their new favorite couple actually got together?
* TearJerker: [[spoiler:Magister Labrid's death]] in the pilot.
** At the end of ''Alone Together'', Reinrassic III choosing to stay on the planet rather than just come back home with Ben. [[spoiler:He gets better fortunately]].
** [[spoiler:Ben's HeroicSacrifice in ''Time Heals''.]]
* TheyWastedAPerfectlyGoodPlot: The whole "Form A Team Of Plumber Kids".
** And even what they did of this plot didn't amount to much. For a series called ''Alien Force'', the only major things thing they did was fight the Highbreed at the end of season 2, get their asses handed to them by Vilgax at the beginning of season 3 and then got [[PutOnTheBus sent off to the Plumber Academy]] after "Above and Beyond". One must wonder what the point to this plot was when pretty much everything important amounted to Ben, Gwen and Kevin (and Max after season 2) doing all the work.
** Some people complained about things that are established, but are just dropped, or otherwise not elaborated upon (Why Ben decided to remove the Omnitrix, which could have tied into him wondering if his job as a hero is worth it, Kevin being EasilyForgiven and almost entirely trusted, among a few other things.).
* TheyChangedItNowItSucks: ''Everything'' has been blamed to be this at least once, from Gwen's alien origins to the Omnitrix's new shape, without forgetting Vilgax's new design, the characters' change of personality (especially Kevin), and the list goes on.
* UglyCute: Argit. There are some people out there (mostly fangirls and furries) who adore him.
** He is '''adored''' by 4chan's /co/, mostly due to this trope.
* UnpopularPopularCharacter: Argit again. In-universe, he is despised by almost everyone, and seems to have people who want him dead in every part of the galaxy. On the fandom side, on the other hand, you would be surprised to see how many fans love him. Even Derrick J. Wyatt, the one in charge of Ben10Omniverse, admitted he thought Argit was the best thing that came out of the Alien Force/Ultimate Alien era.