Ben Tennyson/Synopsis

Note: This article is mainly focused on Ben's human form, articles that are mainly focused on his alien forms can be found.

Original Series
Ben was an unpopular 10 year old boy. Ben saw Cash and J.T. bully Jamie, Ben tried to help Jamie and be the hero but he ended up getting suspended from the nearby tree by his underwear alongside with Jamie. Ben tries to explain Jamie that he was just trying to help, but Jamie rebuked him as his effort just made things worse. Max Tennyson arrives in his Rust Bucket to take Ben on their summer road trip. But then it turns out that Max also brought his cousin, Gwen Tennyson. Ben wasn't happy at all when he heard his cousin was coming with him. They finally arrive at the campsite where Ben walks alone and encounters the Omnitrix. Omnitrix, latches itself onto Ben's (left) wrist. Ben attemps to get it off but fails. Thinking that this is cool, Ben dials the Omnitrix and turns into Heatblast.

After turning into Heatblast for the first time, Ben is terrified but reverts back to Ben later on the episode. After turning into Wildmutt, Ben finally learns how to use the Omnitrix. Ben and the gang decides to help people with the Omnitrix. Ben turns into Diamondhead and defeats the Robot. Later, Ben meets Kevin Levin and helps him using XLR8. Ben and Kevin became good friends but Kevin was planning to hurt others. Ben doesn't likes this idea and tries to turn into Four Arms but ends up being Heatblast instead. Heatblast and Kevin starts to fight but Kevin absorbs Heatblast's DNA. Heatblast times out. Ben goes to the Rustbucket and tries to turn into Stinkfly but turns into Four Arms instead. Kevin absorbs Four Arms' DNA. Four Arms and Tetramand Kevin begins to fight. After fighting, Four Arms times out. Ben tries to help Kevin but Kevin tries to take the Omnitrix which resultsKevin to turn back to normal.

Later in another episode, Ben meets Vilgax and Vilgax successfully captures Ben but when Vilgax tries to take the Omnitrix from Ben but fails. Max reveals that he was a Plumber and the three becomes stronger.

In the episode Framed, Ben waits fro the new Sumo Slammers game. Gwen says that they should go to the bookstore. When they come back out of the store, they see Four Arms attacking people. Gwen Tennyson and Max Tennyson thinks that was Ben. Ben tells them that he was in Rust Bucket. Gwen shows a clip of Four Arms attacking people. So, Ben decides to clear his name by finding who is behind this whole situation.

Ben goes after Four Arms. Gwen Tennyson and Max Tennyson finds Heatblast attacking. Gwen says that he should stop. Heatblast doesn't listents to her. Ben finally comes and proves that he was telling the truth. Heatblast tries to attack Gwen but Ben transforms into Diamondhead and stops him.

Heatblast reveals that he was actually Kevin. After their last fight, Kevin was able to absorb energy from the Omnitrix to transform Ben's alien forms. Four Arms defeats Kevin. Kevin transforms into the fusion of Ben's aliens. In the episode Ghostfreaked Out, Ghostfreak escapes from the Omnitrix, revealing that he was Zs'Skayr who possess Gwen and forces Ben to drop the Sun Gun. Ben drops the Sun Gun, then Zs'Skayr decides to kill Gwen and Max. Ben tries to use the Sun Gun but Zs'Skay tries to possess Ben. Ben quickly turns into Grey Matter and then Zs'Skayr starts to chase after him. Ben exposes Zs'Skayr to sunlight and defeats him.

Omniverse (11 Years Old)
In Omniverse, Ben unlocks a new transformation called Feedback. He gets addicted to using Feedback. Later, Ben meets Malware and defeats him as Diamondhead. Azmuth says that he shouldn't overuse Feedback but Ben don't listens and turns into Feedback to fight Malware. As a result, Malware destroys Feedback. Ben becomes so sad and defeats Malware with his anger.

Off-screen (13-14 Years Old)
In Alien Force, it was revealed that Ben removed the Omnitrix from his wrist off-screen.

Alien Force
In Alien Force, ben continues to live a normal life but then equips the Omnitrix again. After putting back the Omnitrix, the Omnitrix recalibrates and locks Ben's original transformations but gives him 10 new ones. Ben becomes friends with Kevin. Ben also unlocks his most powerful transformation, Alien X.

In the episode Good Copy, Bad Copy, Ben meets Albedo who is Azmuth's former assistant who tried to make a new Omnitrix but became a clone of Ben. Ben and Albedo starts fighting. The Omnitrix causes a feedback that damages Albedo and changes his appearance. Azmuth arrives and sends Albedo to an alien prison.

In the episodes War of the Worlds: Part 1 and Part 2, Azmuth gives Ben the Master Control and Ben saves the world from Highbreed.

Vilgax challenges Ben who tries to hack the Omnitrix with Kevin. This causes aliens to escape from the Omnitrix and Kevin being mutated. Then they capture the aliens. Ben fights with Vilgax who kills Chromastone but gets defeated by Diamondhead.

In the episode The Final Battle: Part 1, Ben fights with Albedo who captures Kevin and Gwen. Ben gives the Omnitrix to Vilgax but says if he doesn't gives the Omnitrix back the Omnitrix will explode and activates the self-destruction mode. Vilgax thinks he is bluffing and lets the Omnitrix explode. Kevin turns back to normal. B Then,Ben does the same thing to Albedo but after proving that he isn't bluffing, Albedo gives the Ultimatrix to Ben. Ben defeats Vilgax with the Ultimatrix by turning into Swampfire and going Ultimate.

Ultimate Alien
Ben's secret identity leaks online. Ben fights with Aggregor who manages to collect all the pieces and rebuilts the Map of Infinity. Kevin absorbs Ultimate Aggregor's energy and becomes the Ultimate Kevin. Ben fights Kevin and defeats him. Ben and the rest cures Kevin. Later, Ben joins Sir George to defeat Dagon. Ben turns into Way Big and then goes Ultimate but gets defeated by Dagon. Vilgax absorbs Dagon and Ben uses the Ascalon to fight him. Ben defeats Vilgax and saves the world once again. Azmuth who is impressed by Ben's action gives him the new Omnitrix.

Omniverse
In Omniverse, Gwen and Kevin lefts the team but can be called. Ben meets his new partner, Rook. Ben gains a better control of Alien X. Ben fights with Malware and re unlocks Feedback. Ben defeats Malware. Ben fights Galactic Gladiator and defeats him using Alien X. Ben also defeats Maltruant.

Uncle Grandpa
In Uncle Grandpa, Ben appears in a short called The Grampies where he makes a cameo.