The main protagonist of the show. Initially a regular ten-year-old kid, Ben Tennyson happened to accidentally stumble upon the Omnitrix, a powerful watch-like alien device, which promptly attached to his wrist. After discovering that it allows him to turn into various alien creatures, each with their own set of powers, he quickly takes advantage of the situation by becoming a Super Hero, dealing with various human, alien, and supernatural threats. Though initially immature and unable to use his powers correctly, he gradually learns, eventually becoming a Living Legend and saving the universe several times.
Badass: The degree of badassitude tends to vary considerably Depending on the Writer, but, despite what Rook thinks, there is a reason he is considered the Savior of the Universe...
Badass Boast: Delivers a quite epic one to the Forever Knights in Ultimate Alien. It scares them into leaving:
"Maybe you have forgotten something: I'm Ben Tennyson, wielder of the most powerful weapon in the universe. I stopped the Highbreed invasion, I defeated Vilgax in hand-to-hand combat, and I've beaten the Forever Knights more times than I can count. Here's what's going to happen: you're going to release these prisoners, you're going to crawl back to wherever you came from, and you're going to stop hunting down aliens because if you don't, I promise, you'll regret it for the rest of your very short lives."
Brought Down to Badass: On occasions, Ben has been separated from the Omnitrix, unable to use it or merely staying in human form. His ten-year-old self was still shown to be quite good using high-tech weapons, and his teenage self has acceptable fighting skills, at one point displaying enough agility and fighting skills to disarm Manny while still in human form.
Took a Level in Badass: He started out as an immature brat with a overpowered weapon he barely had any control over; by the Alien Force/Ultimate Alien era, he has become a Living Legend who can intimidate a Forever King into obeying him with just one Badass Boast.
Beware the Nice Ones: Even though he sometimes acts a bit egocentric and immature, Ben is still a nice, kind-hearted, and deeply altruistic guy. But push his Berserk Button, and you will regret it. Captain Nemesis, Aggregor and Discroll found out the hard way.
Malware even more so. Ben almost killed him when he was eleven, and this wasn't an accident.
Big Brother Mentor: Debatably his position toward Rook in Omniverse, in the sense he is The Leader and the more experienced of the two. Though he is still reluctant to admit it.
Brilliant, but Lazy: It's hinted several times that Ben is smarter than his attitude would suggest; he has an almost photographic memory and can get an extremely good grade when he is working seriously at school. Khyber even admitted at one point he was a "smart kid."
Butt Monkey: In the original series, often as a result of his own actions. It stopped in the Alien Force/Ultimate Alien era, but for some reason, the writers decided to bring it back in Omniverse.
Catchphrase: ""Going Hero" in the original series/It's Hero Time!" Alien Force onwards. He also frequently says "Aw Man!" when a situation is bad.
The Unchosen One: By Azmuth until the finale of Ultimate Alien, where he finally admits Ben is worthy and gives him the final version of the Omnitrix.
Chronic Hero Syndrome: One of his most defining traits from the beginning of the show; even before he got the Omnitrix, Ben had an almost obssessive desire to help people around him whenever he can, sometimes at his own expense. This is why why he Jumped at the Call when he got the Omnitrix. Partially deconstructed in the Alien Force/Ultimate Alien era, where it's shown he takes it so far he is unable to sacrifice anyone (except himself), even if it mean saving millions others. He will always try to find a better way if he can.
Civvie Spandex: Though he does call himself a superhero, Ben doesn't wear any special costume, instead merely using his regular clothes. Some of his aliens forms, on the other hand, wear costum made from his clothes in the Original Series and Omniverse.
Combat Medic: One of the Omnitrix's lesser known powers, revealed in Alien Force, is its ability to repair the damaged DNA of other creatures near its owner. Ben used this to turn the DN Aliens back into full human beings, and he also eventually used it on the Highbreed themselves to repair the damage they'd caused by centuries of inbreeding.
Comes Great Responsibility: Averted in the original series; despite his strong will to help and protect people, Ben would use his powers for personal gain on amusement at any moment (getting revenge on bullies, cheating at games, even once stealing video games), though this often led to the worst possible result, and he draws a line at doing anything that would actually hurt/kill people. His teenage self apparently got over it, but still isn't above using his powers for mundane utility or to have fun.
Cool Bike: The Tenn-Speed, which he built as Jury Rigg using parts from Rook's truck.
Cool Car: Has one in Alien Force and Ultimate Alien.
"LET ME TELL YOU SOMETHING, NEW ALIEN PARTNER THAT I NEVER WANTED IN THE FIRST PLACE BUT I AM GRADUALLY BEGINNING TO LIKE IN SPITE OF MYSELF..."
Destructive Savior: Ben tends to cause massive destruction anytime he practices his super-heroics. In Omniverse, he is mentioned to cause such damage that Mr. Baumann was willing to endure blackmail from criminals rather than take the risk of having him deal with the problem. Granted, considering what some of his forms do, this is a bit justified.
Famed in Story: To the alien underground in Alien Force, then amongst humans as well in Ultimate Alien. By the time of Omniverse, there is a chapter and a half of required study about him at the Plumber Academy.
Future Me Scares Me: Though initially in awe of Ben 10,000, he later calls him on being a Jerkass. Ben 10,000, meanwhile, has a case of I Hate Past Me. Although that was a Ben 10,000 of one of many alternate timelines. Whether Ben would've ended up being that version of Ben 10,000 had he not traveled to the future in the first place is unclear. Averted with the Ultimate Ben 10,000 who was a lot more like his present, teenage self.
Genre Savvy: Depending on the episode, but being a superhero fan to begin with, he has his moments:
When Captain Nemesis challenged him to come and fight him while using kidnapped Julie and Jennifer for a Sadistic Choice, he has Gwen and Kevin coming with him in secret so they can save the girl he won't be able to save of his own.
In "Ultimate Power", he is lucid enough to keep one of his Echo Echo clones hidden in his car while the others goes to fight Kevin. Later in the same episode, he anticipates Darkstar's Chronic Backstabbing Disorder and instructs Cooper into preparing in consequence.
In "The Ultimate Enemy", he immediately deduces that Vilgax would never submit to Diagon unless he has something in his sleeve. He isright.
In "The More Things Change", when Rook raises concern about him not chasing the alien thugs, Ben explains to him that he expects them to report to the Big Bad, who will then send someone against him. While this doesn't exactly happen that way, this was still rather well-thought.
Hero with Bad Publicity: Though only with most adults. Teens and younger kids (and a few adults) seem to think he's absolutely awesome.
Hidden Depths: In Ultimate Alien, it is suggested that the whole Idiot Hero act and constant one-liners as a kid were a coping mechanism so he could deal with having to make life-and-death decisions on a more or less daily basis.
How Do I Shot Web?: Ben initially had a hard time learning how to use the Omnitrix by his own, even causing his first transformation by accident. In the original show, he was able to activate the transformations, but would easily pick up the wrong alien and couldn't decide when he would turn back to normal, forcing him to wait for the time limit to be reached. By Alien Force however, he has learned how to switch between aliens and turn back to normal of his own.
Happens again in Omniverse, where his new Omnitrix possess different commands, forcing him to learn how to use it again.
He has a difficult learning curve when he just obtains a new alien, such as with Cannonbolt. It was downplayed for Alien Force and Ultimate Alien, with Ben figuring out how to use most of the aliens rather fast. Omniverse brings back the learning curve a bit, having problems with Bloxx and Gravattack at first (especially with the latter, due to the fact he had difficulties figuring out what Gravattack could do).
I Hate Past Me: "Hate"'s a strong word, but teen Ben found his 10 year old self to be quite annoying.
Idiot Hero: As a 10-year-old, he was often criticized by those around him to be this, though it could be excused by his youth. He did display the creativity he'd use later on in life on occasions however. His teenage self, while not above doing mistake or letting his ego getting the best of him, usually acts smarter. Usually.
Jerk with a Heart of Gold: He is immature, arrogant, can be quite a Jerkass at times, is not above using his powers for pranks and not unappreciating attention... but if people's lives are on the line, he will throw away everything to save them.
Jerkass Façade: In the Ultimate Alien episode The Forge of Creation, it's stated that the reason Ben acts so arrogant (or at least part of it) is because he's afraid, and it's his way of coping with the stress of being a hero.
Leeroy Jenkins: Zig-Zagged; He tends to act like this sometimes and does get called out for his lack of thought. Other times he displays surprising cunning and a knack for outside-the-box thinking. Most importantly, he is good at adapting himself to the situation when the Omnitrix doesn't give him the form he intended to have.
Living Legend: Gradually becomes this over the course of the series. By Ommniverse, his exploits form a chapter and a half of required reading at the Plumber's Academy.
The Messiah: For all the jerkassery he is capable of, Ben always does his best to help and save people around him.
Mid-Season Upgrade: Ben 10,000 gives Ben all of his locked aliens that he'd used up to that point along with some new ones in the middle of Ultimate Alien's second season. He also brought back Swampfire and Waybig after the two were eroded into dust by Eon.
The Mind Is a Plaything of the Body: Though not clearly specified, it's implied Ben's personality changes according to the form he has. Most of them only cause relatively minor effects (Big Chill is a bit more of a Deadpan Snarker, Spider-Monkey is more excited, etc.), while others will lead to drastic change (Rath is a HammyLeeroy Jenkins, Alien X has three personalities, and Ghostfreak can take over his mind if not careful). In "Frogs of War", his new Incursean form Bullfrag has an outspoken attraction for Princess Attea which he blames on the DNA.
Mouthy Kid: As a 10-year-old. Less so in his teen years.
Older and Wiser: As a teenager. Not much wiser, mind you, as he's still a kid at heart.
This is subverted when he was at Plumber's Academy. He acts dumb but in the end got a 95 out of 100 because just because he acted dumb, didn't mean he wasn't paying attention.
One-Man Army: Literally, as lampshaded in his dialogues with Alan:
Alan: "Well, I guess you too are a monster..."
Ben: "Well, technically, I am an army of monsters..."
Of course, Ben can only use one form at the time, but since most of his aliens are more than powerful enough to deal with entire armies...
His future self in the original series had the Omnitrix's master control unlocked (which let him change into any alien at any moment) and was so effective a crime-fighter he patrolled the entire planet using XLR8, leaving all police and other heroes obsolete. When younger Ben unlocked the control in another episode of the same series, he was able to take on Vilgax and Kevin and fight them equally despite their Villain Team Up. Azmuth unlocked the master control again in the season one finale of Alien Force so Ben could take on the Highbreed and their army of DNAliens.
OOC Is Serious Business: Max knows things are bad when Ben attempts to find and kill Ax Crazy Kevin in the Ultimate Alien season 1 finale without even trying to find a way to cure him of his insanity.
Pride: Deconstructed. By the first season finale of Ultimate Alien, he outright states that he's grown tired of what comes along with his fame. In fact, his constant pestering due to fame and time it took up was revealed to be a major factor for his relationship with Julie taking a big hit.
Red Oni, Blue Oni: The red to Gwen's blue in their childhood. Even more pronounced as red to Rook's blue Omniverse. In Alien Force and Ultimate Alien, though, he becomes the blue to Kevin's red.
Secret Identity: In the original series and Alien Force; interestingly, this is one of the few cases of this trope that completely averts Clark Kenting; Most people thought those aliens creatures were either unrelated to each other or all part of a common team, and no one would suspect it was actually a shapeshifting kid; however, someone did figure it out eventually, leading to his identity becoming public knowledge in Ultimate Alien.
Super Dickery: Season 3 of Alien Force had a whole episode with the Plumber's Helpers attempting to stop an apparently psychotic Ben from killing them and Max while they were trapped on a space station. Of course, it turns out he was just acting like he had gone rogue as part of a test pulled out by Max for the Helpers, but Ben was still scarily good at acting evil.
Super Hero: He is very insistent on being referred to as such.
Voluntary Shapeshifting/Combo Platter Powers: His main ability provided by the Omnitrix is to turn into various alien creatures, each one with its own set of powers. He started out limited to ten forms (hence his surname), only to get more and more as the story goes on. By now, he is assumed to possess more than seventy forms.
His future self has 10,000 alien forms unlocked, and according to Azmuth, the maximum unlockable alien forms in the Alien Force era was of more than one million.
Healing Hands: With the Omnitrix's genetic-repair function. Lost during the Ultimate Alien era due to the Ultimatrix lacking this function. It's unknown if the new Omnitrix got the function again.
Translator Microbes: According to Word Of God, this is the reason he is able to communicate with most alien species he meets and be understandable even in alien forms that should logically not be able to talk human language. Some of them however, like Sixsix or Wildmutt, possess a language too complex or bizarre to be translated.
Multiform Balance: With over 1,000,000 potential aliens with various powers, he could handle any imaginable situation. Theoretically, anyway, thanks to the Omintrix's tendency to be uncooperative and his own reliance on the Indy Ploy above planning.
Both Ben 10,000's have a variation of this, the original series version having the Master Control and the Ultimate Ben10K able to use the powers of all his aliens without changing his human form.
Taught By Experience: While he did take lesson from both Max and the Plumber Academy at various points, he learned most of what he knows of his own since the age of 10.
Took a Level in Dumbass: In the third season of Alien Force. Omniverse put it even further; his original series self practically is a genius by comparison.
Took a Level in Jerkass: In the third season of Alien Force, due to letting his hero status getting the best of him.
To an extent, there are episodes in Omniverse as well where Ben can be a bigger jerk than he ever was in Alien Force. One of the most notable examples being his attitude toward Rook in "Of Predators and Prey part 1". But then it's revealed in part 2 that it was all just an act.
Trademark Favourite Food: As a teenager, he has a fondness for smoothies and to a minor extent chili fries. Ironically, Omniverse reveals he hated smoothies as a preteen before he gained a taste for them with age.
In "A Flash From the Past", when Rook asks whether they should go out for celebratory smoothies, Ben notes that smoothies are for the day time and chili fries are at night.
Transformation Name Announcement: Mainly in Alien Force and Ultimate Alien, though it does pop up on occasion before or after, such as during "Of Predators and Prey" in Omniverse, after transforming into Humungousaur for the first time after many attempts.
True Companions: Himself, Gwen and Kevin in Alien Force and Ultimate Alien. Himself and Rook in Omniverse.
It has been stated in Omniverse that his worst fear now is peacocks, but we have yet to see any demonstration of this.
You Are Not Alone: In Alien Force his Grandpa tells him that Ben cannot go about being a hero alone, and that he needs to put together a team.
This is eventually defied in the episode "Of Predators And Prey: Part 1", where Ben dumps Rook as a partner. To make matters worse, he gets captured by Khyber in the end. And then it's revealed that Ben and Rook planned this all along and only pretended to argue with one another (although Rook didn't catch that part when he went into his "The Reason You Suck" Speech).
Gwendolyn "Gwen" Tennyson
Voiced by: Meagan Smith (as a preteen, Original Series, Destroy All Aliens), Ashley Johnson (as a kid, Omniverse; as a teenager)
All Girls Want Bad Boys: Not in the original show, but she developed an attraction for Kevin in the Alien Force/Ultimate Alien era, eventually ending up in a relationship with him. To be fair, she got interested in his softer side, and would usually get mad after his "bad" side.
Clingy Jealous Girl: defied in Omniverse; when she learns the details about Kevin being engaged with Princess Looma, she actually feels sorry for Looma and blames Kevin for playing her just for a piece of his car.
Hyper Competent Sidekick: Gwen's a prodigy who can basically instantly master anything, be it athletics, academics, and even the Omnitrix in a "What-If" episode, in which she's instantly better at using it than Ben ever was.
Red Oni, Blue Oni: The blue to Ben's red when they were kids, and blue to Kevin's red on their teens.
Sarcastic Devotee: has shades of this in the original series; no matter how much she mocks Ben and criticizes his immaturity, she will always be there to help him when there is actual danger. It goes so far that when Ben had a crush on Kai, Gwen mercilessly mocked him, yet did everything she could to help him and took his defense when Kai treated him like a pet at the end of the episode.
Tsundere: Type A when she was younger. She does care about Ben, but she seems to be near unable to express her affection for him other than by arguing with him. She even mentionned twice that no one can treat him like trash but her. Starting with Alien Force, she becomes a Type B tsundere, but towards Kevin and Ben.
Ben's original Evil Counterpart, second major Nemesis and eventually best friend. Kevin was originally a street troublemaker kid with the ability to absorb energy, who got regularly bullied and considered as a freak. Following a short-lived partnership with Ben he accidentally absorbed energy from the Omnitrix, causing him to mimic Ben's shapeshifting powers, but eventually lost control of them, causing him to end up trapt in the form of agrotesque, chaoticamalgam of Ben's ten original aliens. Blaming Ben for this, he went on a vendetta against him and dedicated himself to try to kill him, only to eventually end up trapped in the Null Void. Following the Time Skip between the original series and Alien Force, Kevin eventually recovered from his psychosis and mutation while in prison, and was able to go back to Earth where he starts working as a Con Man. Events led him to meet with Ben again and be forced to team up with him. Despite a harsh beginning, the two eventually reconcile, and Kevin becomes a valuable ally as well as Gwen's Love Interest.
Anti-Hero: Slides between Type II and Type III constantly. On rare occasion (like when dealing with Ragnarok), he goes Type IV.
Arbitrary Scepticism: in Alien Force; despite living in a world with aliens, Kevin doesn't believe in magic, and keeps saying Gwen's powers come from alien bloodline. He is partially right.
Arch-Enemy: To Ben, in the original series. He was the second most dangerous, preceded only by Vilgax. Notably, he stayed that way in one of the Ben 10,000 alternate futures.
Book Dumb: Plays at this, but is in fact not. Gwen notes that he's good at math and a top-notch engineer, as well as having a knowledge of history. It helps that he literally hasn't gone to school since the age of 11, and most of what he knows he learned on the streets by doing rather than from books by studying.
Heel Face Revolving Door: Went from neutral to evil shortly before his debut, turned good at the start of Alien Force, turned evil again 3/4 through Ultimate Alien's first season, then reverted back to good in the Season Finale, and he's now acting shady again in Omniverse.
Heroic Sacrifice: Non-fatal example. He saves the universe and defeats Aggregor, but at the cost of his sanity.
Heroic Willpower: A flashback in Ultimate Alien reveals he had to concentrate to get back to normal from his transformation in the original series.
Reformed Criminal: Mostly. By his own admission, he's not entirely trustworthy — and a lot of the tech he has in the back of his ride is stolen. Though in his defense, most of the ones he stole from were enemies they were fighting.
The Resenter: When he goes insane again after absorbing the Ultimatrix's power Kevin reveals a great deal of resentment towards Ben. Ben always beat him when they were kids, Ben becomes a world famous superhero while Kevin gets turned into a monster, Ben gets a happy homelife...it's always Ben who gets everything. It's not really made clear how much of this is just the energy-driven insanity speaking and how much of it is real.
Roaring Rampage of Revenge: After being driven insane in Ultimate Alien he decides to go on one of these whenever he's not absorbing other peoples powers.
Omniverse lampshades and justifies it by revealing the reason he was still able to always repair his car despite all the wrecking it took is because he used an indestructible piece of Tetramand tech he got from his engagement with Princess Looma.
Slasher Smile: Does this a lot as Kevin 11 in Ben 10and Ultimate Alien.
Energy Absorption: His original power. Read the spoilers and you'll understand why he never uses it again after the original series.
Combo Platter Powers: Absorbing energy from an alien will cause him to gain some of the alien's characteristics and powers. When absorbing energy directly from the Omnitrix, he will eventually turn into a monstrous, chaotic amalgam of several aliens.
All Your Powers Combined: He at first had Ben's ability to transform, but after getting frustrated with Ben just giving up on him, he turns into an amalgamation of the original ten aliens.
Extraordinaire/Chrome Champion: Capable of turning his body into various metals and/or solid materials that he touches, due to being part Osmosian. Ultimate Alien reveals he learned this from Quarrel.
Rubber Man: He once turned his body rubber after touching the tires of his car.
Midseason Upgrade: Gets shapeshifting powers in The Vengeance Of Vilgax which make him stronger, which he retains even after being restored to human form. Made a plot point in that if he hadn't got them, they'd have been unable to save the world from Hex. This really helps increase his usefulness to the team.
Took a Level in Jerkass: Omniverse, possibly, in an attempt of Character Rerailment, portrays him as more of jerk by revealing his backstory with Princess Looma and having him pulling out a Batman Gambit to get rid of her by giving her to Ben. Even Argit seems to think he exagerates.
Troubling Unchildlike Behavior: In the original series. It's quite disturbing to see a 11 years old kid trying to commit mass-murder to get money, and later attempting to kill gruesomely a 10 years old kid.
Adorkable: While he is a impressively effective fighter, he is socially awkward due to his lack of knowledge of Earth's customs and not understanding sarcasm.
Arbitrary Skepticism: Despite being an alien in a world with various alien species running around, high-tech weapons and many other things, he believes Alien X is nothing more than a legend. He does see him in "So Long and Thanks For The Smoothies?" but his memory got erased when Alien X had to recreate the whole universe.
Ascended Fanboy: He admires Ben; his personal reason for coming was to see if Ben lived up to the legend.
Badass: When first introduced, he neutralizes three alien criminals of his own with almost zero effort.
Badass Normal: Unlike most alien species in the series, he lacks any ability that could be considered a super-power by human standards, and relies solely on his tech and Plumber training. Doesn't stop him from kicking ass.
Badass Bookworm: He is extremely well read and knowledgeable about galactic history, science, and technology.
By-the-Book Cop: Rook is described as "all training no experience". He also treated Ben as a superior rather than like a friend when they first met, acting respectful toward him and calling him "Sir", until Ben asked him to just call him Ben. However, unlike the usual exemple, he is less experienced than Ben.
Captain Obvious: Tends to point out obvious things to Ben quite frequently.
Foil: To Ben; he is a By-the-Book Cop with no actual experience, in contrast with Ben being Taught By Experience with little training. Moreover, he relies on technology, while Ben relies on alien biological abilities. Word Of God admitted this was the guiding purpose in his design.
Hyper Competent Sidekick: Played with; Ben is far from incompetent and has much more experience, but Rook still displays much more impressive fighting skills and ways to deal with situations.
Deconstructed in "Of Predators and Prey"; after going around with Ben for a while, he ends up believing Ben doesn't live up the legend and only saved the universe because he had people around to help him. This, plus Ben's Jerkass tendencies, led them to argue and split up, allowing Khyber to finally attack Ben alone. While this ultimately seems to have just been a ploy to lure out Khyber, Rook admits that he was actually quite serious during his "The Reason You Suck" Speech.
In the Hood: He is introduced as a customer wearing a hood.
Naïve Newcomer: Despite having read a lot about his task as a Plumber and trained extensively, Rook had never actually fought criminals before being assigned to Ben. As a result, he is naive and inexperianced.
Nice Guy: In notable contrast with Gwen's and Kevin's snarkyness in the original series and Alien Force respectively, Rook appears to be a nice person who genuinely admires and respect Ben.
"How many times you have saved this Universe? By yourself? Zero! Everytimes, there have always be someone there to help you! [...] I have been there! I have already saved you countless times, and I have only been with you a few weeks! I am surprised you made it this far!"
Take note that, Part 2 of "Of Predators and Prey" shows that Ben and Rook were pretending to fight, however Rook didn't get part of that memo and was somewhat honest about that whole "saving the universe by yourself" bit.
Adorkable: Back when he first met Verdona, he managed to hit this trope while still being badass. The early 1960s setting- so early that one would think it to be fifties if not for the Kennedy reference- definitely helped.
Adults Are Useless: averted. He has the experience, the tools, and the ability to take down villains with or without his grandchildren's help. He knows about the Omnitrix from the beginning, does his best to help, and, when informed by his granchildren about aliens or other weird phenomenon, believes them.
Badass: one of the biggest badasses in the franchise.
Lethal Chef: he is not exactly a bad cook, he just has very... weird tastes in matter of food and ingredients (termites and squid to give examples). Gwen, Ben and most regular humans are creeped out just by looking at this, but some aliens, like Xylene and Rook, are quite found of it.
Missed the Call: The Omnitrix was sent to Earth with the intent of Max finding it, not Ben.
Morality Chain: sort of, to Ben; at least, he played a large part into making Ben a proper hero; "Store 23" shows us an alternate reality where he died just before Ben got the Omnitrix, causing Ben to become even more narcissistic than he already was, create a Telereality show focused around him, treat all aliens as evil and almost cross the Moral Event Horizon by attempting to rip his dimension's Azmuth in half.