Ben Tennyson

Glen Murakami's original concepts for 15-year-old Ben Tennyson from Ben 10: Alien Force.

Ben 10 was created by Man of Action (consisting of comic book creators Duncan Rouleau, Joe Casey, Joe Kelly, and Steven T. Seagle) and was produced by Cartoon Network Studios. The group worked on the concept of Ben 10 and its title character roughly three years before Cartoon Network picked up the series. Dave Johnson also helped in the design development.[4] Early on in development, it was decided that a villain would be within the Omnitrix.[5] After Ghostfreak was created the creators added dialogue into the first season to give the audience that there is something more to Ghostfreak.[6] Originally Cannonbolt, the 11th alien transformation in the series, was going to be in the original set of aliens, but was replaced with Ghostfreak.[6]

When doing test animations for the series the first alien transformation to be tested was Four Arms. It was the most popular transformation out of all the aliens for "Man of Action".[6] Many of the unused designs for Upchuck were recycled in the episode "Ben 10,000" as two of Ben's aliens "Spitter" and "Arctiguana", and as villain Sploot. Steven E. Gordon worked on an early version of the series. His concept work reveals that Ben Tennyson was originally going to be a red-headed young boy. Gordon also has early designs of the Omnitrix which look more like a watch than the final version, as well as different designs and names for the alien transformations.[7] Some of the early names for the Omnitrix transformations were "StrongGuy", "Inferno", "RazorJaws", "Dragonfly", "Plantguy", and "Digger". Some of the early designs for the aliens are more human and superheroic, similar to Dial H For Hero.[7] The character's middle name, Kirby, was named as a reference to comic book artist Jack Kirby.[8] Initial concepts for Ben's Alien Force and Ultimate Alien designs were made by Glen Murakami. His head and hair were reworked by Glenn Wong, who also gave him his green jacket, while colors were added by Chris Hooten.[9][10]

You think I don't know? When it's hero time, if I mess up, somebody could die. From what you told me, if we mess up this time, everybody could die... Maybe that's too much to have in your head when you have to win. Maybe if I pretend everything is a big joke, when the time comes, I'll be able to do what I have to do.

— 10 year old Ben to 17 year old Kevin asking him to be serious.[11]

Initially cocky, childish, and selfish, Ben's immaturity and attention-seeking behavior often led him to joke around, regardless of the situation. His allies often criticized his attitude, unaware of the fact that he used humor to mask his fears. Despite some childish attitude, he was heroic, caring and generally good-natured, always willing to save others at any time even at the risk of himself.

Over the years, Ben has displayed good leadership skills, as well as the ability to adapt his attitude to a situation, becoming serious when it's called for. He became more mature, responsible and sensible. He's kind-hearted, willing to sacrifice even his own life for others. His idealistic views and unwillingness to compromise his values – aspects condemned by Azmuth, yet commended by others – sometimes drive him to act against reason, such as helping his enemies if they need it (most remarkably Vilgax).[12] Professor Paradox has praised Ben's good nature, going so far as to say he had the gift to make the right choices at the right moments even Azmuth himself states that Ben ultimately always does the right thing.[11] Also, Ben doesn't give up and wouldn't let anyone stop him from doing what's right for those in need, especially his family, friends and mentors, or to bring enemies down, even when he once got a broken arm.[13]

However, when Ben fails to save someone, or if someone gets hurt because of his failures, he becomes angry and much more violent. Perhaps the most notable of these instances is when Kevin willingly mutated himself to succeed where Ben had failed and stop Aggregor, Ben was set on killing Kevin, even fighting Gwen when she refused to help him.[14] He also threatened to hunt down and destroy the Forever Knights once making Driscoll promise to cease the hunting of aliens.[15]

Though often stated to be silly or unintelligent because of his immaturity, Ben is cunning and resourceful when needed, quickly adapting when the Omnitrix doesn't provide him with the alien he wanted.

Later on, Ben starts thinking of himself as more of a superhero than a Plumber, often remarking that he's not a cop, but a superhero.[16] Although he once again became cocky, he retained his selfless and heroic nature.

As Ben 10,000:

At some point in his future, Ben became so strict, cynical, and serious about the hero business to the point where it is almost obsessive. He rarely turned back to his human form, spending most of his time in alien form, skimming his patrol routes, and brutalizing criminals as quickly as he could. He also stopped naming his aliens. He stayed this serious for years until he met and had a talk with his younger self, after which Ben lightens up and he starts naming his aliens again. He likes to spend time with his son and, while he tries to be close to him, Ben sometimes doubts his abilities as a parent and becomes over-protective. He can also be somewhat obtuse, not realizing where his son got his attitude from and grasping the obvious. While Ben is a lot older, he still has a teasing side, jokingly calling his cousin Gwen "dweeb".

Ben possesses a commendable amount of bravery and courage. Despite his change to a more light-hearted and relaxed person, Ben 10,000 has a ferocious temper that returns him to the more aggressive and grim personage he displayed before.

• List of Ben 10 characters
• Robby Reed and Chris King and Vicki Grant