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.

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.

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.

The gang helps the prince of the arachna-chimps regain power

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.

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.

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.

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

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.

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.

While Ben has a date with Julie, it is soon ruined when an alien named Ship makes trouble at the local fair.

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.

Vilgax, after conquering 10 planets, comes to Earth to destroy Ben.

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.

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.

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, 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.

Ship's owner decides he wants him back and hires some repo men to retrieve him. Ben and Kevin go to court to take care of things legally, leaving Gwen and Julie to face the repo men.

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.

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 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.

A bounty hunter tries to remove the Omnitrix from Ben.

Freelance young Plumbers mistake Ben and his team as a threat.

The Forever Knights secure a weapon in hopes of aiding them slay a dragon they have held captive.

Kevin makes a temporary truce with Darkstar to retrieve an artifact that will return them into their former selves.

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.

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.