Average kid, ten year old Ben Tennyson, his Grandpa Max and his cousin Gwen's summer of adventure takes an odd turn when Ben discovers a watch like object that has been jettisoned from alien spacecraft high above the Earth.

Ben must fight Dr. Animo, a crazed scientist who has a DNA-altering device.

Ben has his hands full with a giant sea monster and an evil poacher.

Ben must rescue his aunt and grandfather when they are held hostage by shape-shifting aliens.

Ben is pursued by three bounty hunters sent by Vilgax to steal the Omnitrix.

Ben accidentally releases creatures made of electric energy and must use his own powers to recapture them.

Ben meets a mutant who can absorb any form of energy and may be after the Omnitrix.

Ben clashes with a female gang member who's become part cyborg.

Ben discovers an evil circus that's headed by a psychic vampire clown named Zombozo.

Ben battles a sorcerer who possesses a number of charms, and Gwen suddenly becomes a superhero when one of the charms falls into her hands.

Ben gets revenge on an amusement-park attendant who said he was too small to go on a ride.

Ben's summer cold causes strange physical changes in his alien personas.

Vilgax tries to get the Omnitrix for himself while Grandpa Max's strange past becomes known, causing a showdown between Vilgax and the Tennyson family.

After the battle with Vilgax, Grandpa Max retells his story to Ben about his past. He was with an organization that was not known to exist, referred to as "The Plumbers," a group of people who track down extraterrestrial life. Meanwhile, they meet Phil, an old partner of Grandpa Max. But they soon find out that he steals a device, called the Null Void Projector, to selfishly use it to make money by appearing to capture aliens that he alone released himself.

At Yellowstone Park, Ben and Gwen inadvertently discover a new form on the Omnitrix: Cannon Bolt, an armadillo-like alien that Ben isn't too fond of. Soon after, a meteor comes crashing down to the park, containing a planet-devouring, tick-like alien. On top of that, three other aliens arrive with it, and worship it as their savior, the "Great One." Powerless to stop the planet-eater with his regular forms, Ben must rely on a new form he knows nothing about.

At a city, Ben, Gwen, and Grandpa Max are waiting outside a video game store to purchase the newly-released Sumo Slammer video game. Gwen and Grandpa Max go the book store, but when they return to check on him, Four Arms comes out of the store by force. They return to the RV, and find that Ben is already there. Gwen yells at Ben for what he's done, but he has no clue of what she's talking about. But as she gives direct evidence that Four Arms was attacking the city, Ben heads out to find the perpetrator, using the identity of his aliens to ruin his current reputation as a hero.

In this "how 'bout?" episode, Gwen gets the Omnitrix and the power that comes with it.

In the middle of nowhere, Ben, as Diamond Head, fights Kevin 11, who is still in his mutated form. As they fight, they are taken to a ship, where a battle between different aliens are held. But when a mechanical droid named Slix decides to create a bond with Ben and Kevin as a team, they immediately turn his idea down. But with no choice, they must find a way out. Will Ben and Kevin learn the importance of teamwork?

At a museum, Ben sits and reads a comic, daydreaming about himself as a super hero. As Gwen interrupts him, she is not happy how Ben treats the artwork. His day has been a bore, but when an alien vessel arrives, an alien named Volcanus and the bounty hunter Sixsix come to pursue the Biocenthium alloy to complete a mixture with Element X to create a bomb, strong enough to destroy a whole solar system. Suddenly, Ben meets The Galactic Enforcers, a group of three who serve in protecting the galaxy under the conduct code. Ben is intrigued by their heroic appearance, but are they really something to be looking up to?

When Ben and Gwen argue over a birthday party to occur in the next few months, Grandpa Max is distracted by their quarreling and almost hits a young boy camper. To ensure the boy's life, they head to Camp Opinicon, only to find no people around. As they investigate the premises, they find twins, whom were also hiding from something that may have a connection to the lifeless camp. Grandpa Max readies to leave the area with the children, only to find that the RV's engine is clogged with a mysterious fungus. While the kids take in shelter in a nearby cabin, Grandpa Max is captured. Now Ben must come to the rescue to discover a new alien form, as well as a way to destroy the evil alien Myceloid Monsters and their Fungal Master, and learn the benefits of what sharing can do.

In Texas, a group of men discover a mysterious mask belonging to Ah Puch, the Mayan god of death and destruction. The mask is the key to the ultimate weapon in the world, known as the Sword of Ekchuah. However, when Grandpa Max and his grandkids learn that the mask is discovered, he impatiently sets out to obtain the mask, so that it does not fall in the wrong hands. Unfortunately, they find out that Enoch of The Organization is after it as well. The kids worry of how Grandpa Max has become, but with Enoch in the way, will Grandpa Max find the sword before him?

Hex's niece, Charmcaster, enters the underground prison he's held at to release him out of his cell. With her help, Hex was able to regain most of his powers after being given his magical staff. Meanwhile, Ben, Gwen, and Grandpa Max head to a magic convention held in Las Vegas, and in there, Gwen finds the legendary Keystone of Bazell. With it, she gains the powers of Lucky Girl once again, but will it last after finding out that Hex and his niece are after it?

Our heroes ride a jet belonging to Grandpa Max's old Friend, Donovan Grand Smith, who owns an underwater resort. At the entrance, they receive a warm welcome from Donovan himself, though they also meet with his grandson, Edwin, who didn't seem to be excited about their guests. Later, when Edwin, Ben, and Gwen enter the Undersea Manta Ray, a giant submarine, they encounter strange aliens that threatened to destroy the whole resort. While the kids find a way to cooperate with each other to find the source that lures them in, Donovan himself learns a few lessons in how to bond better with his grandson.

A terrorizing nightmare of Ghostfreak is half the trouble for an unnerved Ben, as a tour of an important academy that Gwen wishes to attend is disturbed by the uncanny alien's manifestations and the antics of Acid Breath, Frightwig, and Thumbskull.

The Tennysons arrive at a swamp, where a festivities of Gatorfest start first thing the next day. Gwen finds Ben playing around with the Omnitrix, and she warns him that it may create unusual problems. Without heeding Max and Gwen's warning, he pops the face out, and the Omnitrix acts up. Right away, something was wrong, though it was gone unnoticed, at least, until the next day. Gator-fest was going along well, but the giant frog of Dr. Animo comes in to disrupt it. Dr. Animo has returned, and he wants to take revenge on Ben. But when Ben goes alien, he transforms into a hybrid alien with unbalanced attributes. Will Ben ever learn his lesson in listening for a change?

The Megacruiser flies solo in space, and inside Kevin examines the giant ice block found in space. Inside the mass, held Vilgax, and Kevin underestimated his current situation. He was very much alive and well, and they soon create a partnership after learning that they were both after the same person. On Earth, Ben plays around with the Omnitrix, hoping to find a better way of controlling it. Eventually, he finds the master control of the Omnitrix, giving him the ability to alternate between aliens, as well as prolong his duration with a form. Although his discovery has given him a stronger advantage, will it be enough to stop the danger that lies ahead?

When Gwen is abducted, Ben as XLR8 follows her abductor to the future where they discovered that her abductor is the future Gwen and they discover his future version of Ben and Grandpa Max. In the future, Dr. Animo revives Vilgax and plots to open the Null Void chamber. Both Bens must work together to stop them.

When Ben is hypnotized, he begins breaking the law while sleepwalking. Once the evil hypnotist called Sublimino discovers the aliens at his disposal, he plots to put hundreds of people under his control forever.

Dressed as Pilgrims, to honor their history, while in the streets of Salem, MA, Ben, Gwen, and Grandpa Max witness an explosion of a nearby building. But when Ben rushes to the rescue, Charmcaster is there waiting with a spell to take over Ben's body and the Omnitrix. Only things go awry and Gwen and Charmcaster switch bodies. Gwen goes to prison and the sorceress is brewing a plan to gain the Omnitrix. Now Gwen must find the way to get out of prison, alert her family against Charmcaster, and get her own body back using every trick up her sleeve... or Charmcaster's.

Ben, Grandpa Max, and Gwen come upon a bizarre Christmas theme park run by an evil entity who thinks Grandpa Max is Santa Claus and proceeds to trap him.

Ben, as Wildvine, is fighting against an evil werewolf and is bitten. The Omnitrix times out and Ben turns back to his human form. Then, when the werewolf hits the Omnitrix, it starts to mess up and act weird. After all of this, Ben starts to get a crush on a girl that he meets. But things change, as Ben slowly starts to turn into a werewolf himself.

The Tennysons stay in as it rains outside, and Ben plays a video game to pass the time by. When Gwen decides to join in, Ben is jealous of how she's a far superior player. Instead, Ben decides to transform to Upgrade, and merges with the game console. Gwen makes an attempt at shaking him off, but suddenly, a lightning strike causes them to transfer into the video game itself. The only way Ben can use the Omnitrix is to find coins with the different aliens on it. To get out, they must find the Upgrade coin before an evil being uses it to escape into the real world.

Ben's alien heroes are starring in a silly network cartoon called Super Alien Hero Buddy Adventures and his favorite action hero Kangaroo Commando has been pulled off the air by the same network, so Ben tries to get him back on television and get credit for the alien heroes.

In order for Ben and Gwen to learn the value of hard work, Grandpa Max takes them to a farm. Meanwhile, an alien mummy arrives to uncover a rare and dangerous element.

While attending the Little League World Series to see his home team play, Ben discovers that the opponents are actually robots posing as kids. They also have plans to replace the President with one, as well.

Grandpa Max takes the kids to Chicago to see one of his favorite band, Shag Carpeting. The kids meet a weather reporter who forecasts the weather with a robot named S.A.M. He uses the robot to create rain, but a giant creature forms! Ben quickly takes care of it. The reporter tries to destroy S.A.M., but he convinces him not to. S.A.M. then goes into the sky and begins to cause chaos. The reporter tries to stop it again, but he is no longer in control. Can Ben destroy the robot and save a city from disaster?

While driving on a Florida highway, a bus of escaped felons rams into the RV. Ben transforms into Stinkfly (though not intentionally) and tries to stop them. With a little help from Grandpa's handy driving, and a magic spell from Gwen, the felons are put back in jail. On the news, the Tennyson's hear about purple lightning delaying a space shuttle launch. Remembering the lightning from the encounter with the werewolf and mummy aliens, they head to Cape Canaveral. At the Space Center, Ben comes under attack by the werewolf and mummy aliens, and new Frankenstein alien. However, why is the purple lightning occurring, and what ties does it have to an old "friend"?

Ghostfreak's return spells disaster for our heroes. Grandpa Max and Gwen must deal with the mummy alien in space while Ben deals with Ghostfreak and Dr. Vicktor on Earth. Ghostfreak then reveals his master plan: he plans to blanket the Earth with Coronium so that sunlight will not reach the planet so that he may rule. With the power of a new alien in the watch, can Ben stop Ghostfreak, and save Grandpa and Gwen?

While snowmobiling, two guys accidentally release an alien named Xylene from a strange container. At a park, Ben (as Wildmutt) steals Gwen's kite, so she casts a spell to make dogs attracted to him. Grandpa Max seems sad to be in St. Louis since it is where he met his wife. Xylene attacks, and Grandpa Max comes to defend, only to recognize her. Xylene reveals that she came to find the Omnitrix since she lost it when Vilgax attacked her ship. While Grandpa Max and Xylene talk about the past, a robot emerges from the area where Xylene was and attacks Ben and Gwen. The mechadroid attacks twice, taking Grandpa Max with him. Now Ben must work with Xylene (to his dismay) to save Grandpa Max.

Enoch and the Forever Knights return, putting Ben in a dream world where he's tricked into having the perfect day. However, his dream quickly turns into a nightmare.

Ben gains another Omnitrix hero to use, which he calls Ditto. Gwen can't stand being around the multiplying Dittos, and they end up giving her headaches. The Dittos, though, prove to be real helpful against Dr. Animo and his multiplying Stinkflies after he extracted some of Ditto's DNA.

After being in contact with water from the Fountain of Youth, Grandpa Max and Ben are reverted to being kids again. Now, Gwen is left to take care of them while stopping Hex from finding the fountain's source.

Ben, Gwen, and Grandpa Max attend a family wedding. During the ceremony, a strange alien attacks. Will the two ever finish this strange wedding?

During a battle with Dr. Animo, the Omnitrix is accidentally set to self-destruct. In order to stop it, Ben, Gwen, and Tetrax travel across space to track down the Omnitrix's creator, Azmuth.

During a battle with Dr. Animo, the Omnitrix is accidentally set to self-destruct. In order to stop it, Ben, Gwen, and Tetrax travel across space to track down the Omnitrix's creator, Azmuth.

During a battle with Dr. Animo, the Omnitrix is accidentally set to self-destruct. In order to stop it, Ben, Gwen, and Tetrax travel across space to track down the Omnitrix's creator, Azmuth.

While on a desert highway, the RV gets stolen by a group of modern-day pirates, who use it to go on a robbery.

When Ben accidentally breaks Gwen's laptop, he participates in the "Ultimate Wrestling Competition" as Four Arms to get the prize money for a new laptop to replace Gwen's broken one.

In the future, Ben gives his son, Ken, an Omnitrix for his 10th birthday. However, Ben will have to learn to trust him with that power.

Ben, Gwen, Cooper and Grandpa Max face their last battle ever against the villains they have encountered and they will battle to get the world's most powerful energy source.

The Forever King sets his plan in motion and recruits the most powerful enemies Ben has ever faced in order to steal the world's most powerful energy source.

The summer finally ends. Ben and Gwen have to go back to their normal lives. Grandpa Max tells Ben to keep the Omnitrix a secret from everyone, even his parents. Ben agrees, but Vilgax arrives and he'll stop at nothing to get the Omnitrix.