Ben discovers that the Forever Knights are trading weapons with the DNAliens, while at the same time, Grandpa Max has mysteriously gone missing. He decides to return the Omnitrix on his wrist and go hero once again.
Ben, Gwen, and Kevin follow a lead that takes them to a secret base in the desert. There they hope to find Grandpa Max but instead find a Highbreed spaceship with a giant cannon.
Gwen discovers that Grandpa Max's badge is able to signal other Plumbers. However, by using it, they meet up with a familiar face, a pyronite.
Kevin shatters Ben and Gwen's trust when he steals the Rust Bucket to sell for alien technology on the black market.
Grandpa Max leaves Ben a series of instructions to contact a team of heroes. Things go the wrong direction when they soon find them.
Gwen's older brother, Ken, is suddenly missing. As they look, they encounter a surprise leading to a shocking secret from the DNAliens.
While Ben has a date with Julie, it is soon ruined when an alien named Ship makes trouble at the local fair.
When Ben and Gwen learn that their grandmother Verdona is an alien being, Verdona insists that Gwen should come along with her to her home planet and improve her abilities. With this, Gwen is faced with a difficult decision between a human and alien life.
When Ben stands up to Cash and JT, they soon discover a robotic gauntlet from Kevin's vehicle. With it, Cash decides to get back on Ben, although this time, it's more than just a joke.
A time experiment in the 1950s sends a bizarre monster to Ben's time. Now Ben, Gwen, and Kevin must team up with Paradox, a time traveling hero, to face off against the unstoppable creature.
The Forever Knights secure a weapon in hopes of aiding them slay a dragon they have held captive.
Freelance young Plumbers mistake Ben and his team as a threat.
An alien emperor plans to destroy the planet Earth for kidnapping his daughter. In order to save the planet, Ben must uncover the secrets of Alien X.
A new villain comes into town, his name is Darkstar, he commits some crimes and gets the team's attention fast
During a battle Ben and an alien commander are teleported to a distant world. They must put their differences aside if they're going to have any chance of finding a way to return to Earth.
An alien impersonates Ben with hopes of using his Omnitrix to annihilate him.
Kevin asks Gwen to the school dance; Ben fears he's losing control of the Omnitrix.
Cooper is kidnapped by the DNAliens, who want him to build a mystery arch.
To find and destroy the alien dragon species, the Forever Knights capture Ship to control a starship they built out of alien technology to locate their homeworld and destroy them.
When Ben's parents discover his ability to turn into aliens, they forbid him from using the Omnitrix and later ground him from using it again. Eventually Gwen is grounded too leaving Kevin to stop the DNAliens.
After Gwen receives an S.O.S. from Helen, Ben must go into the Null Void to save her and Manny. Once there, he must find The Wrench in order to stop D'Void, who happens to be Ben's old enemy Dr. Animo
Ben and the gang rescue a runaway prisoner of the DNAliens.
The gang helps the prince of the arachna-chimps regain power
Ben cares for a baby monster and helps locate its parents before the DNAliens find it.
Ben, Gwen and Kevin gather their allies to counter the threat of the incoming Highbreed fleet. Azmuth reveals a secret about the Omnitrix.
Ben goes to the HighBreeds' world in an attempt to stop their attack on Earth.
Vilgax, after conquering 10 planets, comes to Earth to destroy Ben.
Ben, Gwen and Kevin race to collect the Omnitrix's missing forms and make it to the battle with Vilgax on time. Meanwhile, Kevin discovers that his new transformation has some benefits.
Ben, Gwen and Kevin discover that Vulkanus is planning to drill the center of the Earth and drop a bomb into the hole. Destroying the planet.
A species of goat-like aliens comes to Earth for a popcorn festival. Ben, Gwen, and Kevin have a big problem when one of the aliens eats meat and turns into a monster.
An alien named Probity seeks help from Ben to stop the on-going war on her home planet.
Repo men are hired to return Ship to his parent.
A bounty hunter tries to remove the Omnitrix from Ben.
A series of earthquakes awakens a HighBreed officer who has been hibernating deep under the earth’s surface. He believes the HighBreed have lost the war and activates a fail safe device that is programmed to destroy. Ben must now work together with Gwen and Kevin not only to save Grandpa Max, but also the world from this "giant" problem.
Kevin is beginning to lose all hope that he will someday return to his human self. He then meets a girl who doesn't seem to mind the form he is in. Kevin finds himself under her spell, quite literally, as Charmcaster has come back to exact revenge on Ben and Gwen. Kevin, under Charmcaster's spell, has no choice but to obey his master and destroy Ben and Gwen.
Vilgax promises Ghostfreak to spring him out of prison as long as he tells him the secrets of the Omnitrix, but when Ghostfreak betrays him and turns his people into his minions, Vilgax comes to Earth and asks for Ben, Gwen and Kevin's help to get rid of Ghostfreak.
Ben and friends face there toughest challenge yet, as the cartoon comes to life. Ben, Kevin, Gwen and Max have got some new alien tech to deal with, but it's nothing like they've ever seen before. Can they handle it, as friendships are weakened, whilst romance blooms. Trust is the question in hand, but who can be trusted is the answer.
Kevin makes a temporary truce with Darkstar to retrieve an artifact that will return them into their former selves.
Ben, Kevin and Gwen come across an alien box that can forms into a robotic version of whatever it sees. It power becomes a liability when the Vreedle brothers decide to take the box for themselves.
Zaw-Veenull asks Ben to deliver Prince Tiffin to Jarret in order to keep peace between the two species. Shortly, after their trip in space, the Omnitrix malfunctions and turns Ben into an Appoplexian named Rath who wants to fight anything that breathes.
The Omnitrix transports Ben, Gwen, and Kevin to a planet called Primus, which turns out to have been created by Azmuth. They must stop Vilgax from stopping the Omnitrix at its source.
Despite being warned by Paradox, Gwen travels back in time to prevent the accident that turned Kevin into a monster from ever happening. Gwen returns to the present only to find that her time traveling caused a series of events that led to Hex ruling the world.
While sick, Ben is visited by old friend Tetrax, who demands that Ben hand over Chromastone.
The Plumber's Helpers are called upon by Grandpa Max to rescue him from an abandoned space station where he's being attacked by Ben! The team must now find a way to work together as they try to save Max, stop Ben, and keep the space station from crashing to Earth.
Kevin returns home to find his house ransacked, so he enlists Ben and Gwen's help to find out who did it and why. They soon cross paths with Ragnarok, a deadly criminal who recently broke free from the Null Void and is in search of a special key. Kevin is intent on stopping Ragnarok from obtaining the special key, especially after he learns the truth about Ragnarok and his father.
Albedo has stolen the Ultimatrix from Azmuth and has used it to kidnap Gwen and Kevin. Ben goes to face Albedo and rescue his friends when he quickly discovers that Albedo has been working in conjunction with Vilgax. Ben is defeated by the pair and gives up the Omnitrix to save himself and his friends.
Powerless, Ben goes aboard Vilgax's ship and faces off with Vilgax to stop his invasion of Earth in their final battle. Albedo gives Ben the Ultimatrix and Ben gets his old aliens and their evolved forms.
