Ben meets the ones responsible for his intergalactic TV show (mentioned back in "Bros in Space"), and the crew who makes this Ben 10 actor more famous than Ben himself, with Ben frustrated with this show on the air and taking his fame, Simian ends up hiring an alien collector known as Collectimus who turns things into training cards for his collection. He ends up taking Simian into his deck and in order to save the actor, and the Earth, Ben and Rook must take him down.

As Ben and Rook go on a double date with Ester (the Kraaho) and Rayona (Rook's girlfriend back home), they encounter Nyancy Chan, who places Ben (as Rath) under her trance and uses him in a crime spree. Meanwhile Princesses Looma and Attea are at odds about who will get to legally marry Ben's alien forms: Four Arms and Bullfrag.

Zs'Skayr and his allies awaken the great evil Lord Transyl, where he asks to make an alliance to rule the universe, but just as they team up, they manage to hypnotize everyone on Anur Transyl, and Ben's team. Now with Ben's newest alien Whampire, Ben and Hobble (the remaining people left) must discover a way to defeat Lord Transyl, save everyone, and must fix their ship in order to get back to Earth.

Still stranded on Anur Transyl, Ben suffers from a serious zit problem that grows worse with each time he uses the Omnitrix. At the same time, Charmcaster proposes an alliance to defeat Zs'Skayr, since he stole the Alpha Rune from her. Also, a female Trasylian alien named Viktoria develops a crush on Ben, due to his terrible acne.

As Ben, Rook, Rad, and Hobble fly through the Anur System to deliver something before they end up crashing into Anur Transyl, needing a device to power-up their engine. But as they walk through the planet, due to Anur Transyl being all but closed to the rest of the universe, the Halloweenish residents see Ben and his group as the monsters. But besides the angry mob and his friends being abducted by a Thep Khufan named Kupuhulu, Ben learns that Zs'Skayr (Ghostfreak's real name) has orchestrated the delivery to bring himself and the mentally restored Dr. Viktor back to their home system with revenge as an added bonus. Though his team got the upper hand, Ben ends up breaking the replacement device with them now stranded on Anur Transyl.

Dr. Animo from the Future return to go to the present to break Dr. Animo out of prison, and to steal something from the SACT so that they can populate and rule the Earth with Mutant Animals, and in order for Ben and Rook to stop him, they get assistance off someone from the future currently known as Chrono-Spanner.

Ben's childhood crush, Kai Green, asks Ben and Rook for help when her grandfather is kidnapped by the Forever Knights who are after a mysterious sword all the way in London hidden in a secret room under the river. Could what the knights seek be King Arthur's mythical blade, Excalibur?

Bill Gacks, an (actual) human plumber who resembles Vilgax (due to his beard), accidentally activates a weapon Vilgax set to attack Bellwood while fixing Pakmar's plumbing in Undertown. When Psyphon returns, he believes Bill is Vilgax, and, elated that his master has returned, pledges to help him in any way to destroy Bellwood. Meanwhile Ben and Rook try to stop Vilgax's squid monsters that the weapon accidentally released.

After Gwen as Lucky Girl beats Punchinello, Ben and Rook visit her and Kevin at college, but Darkstar (disguised as a student: Dante) gets revenge by using Charmcaster's rock monsters, and creates a cult in order to use Gwen to open up a portal to Ledgerdomain to absorb all the mana to become even powerful. Meanwhile Ben has some problems with the Omnitrix when it only wants to give him Ghostfreak.

After two uneventful weeks, Ben is edgey and desperately hoping for something wrong to happen. He and Rook investigate a circus, which Ben decides to stay out of while Rook enjoys the show; however, he comes out looking like a clown, repeating "Come one, come all." Ben gets him to Plumber HQ, suspecting that Zombozo is up to his old tricks; however, Zombozo has escaped his cell and the number of zombie clowns is growing. Now Ben must try to overcome his fear of clowns so that he can save the people of Bellwood.