Ben 10

Aunt Vera    

Vera is Ben's aunt, a stereotypical "senior citizen" who lives in a retirement community in the desert. The specific location is unclear. She seems to have a similar cooking taste to Max, making food that, while not as strange, is certainly unusual even for the current day and age. Her cooking habits are similar to those of women in the 1950's in that she makes gelatin molds with odd contents, such as pork chops.

It is hinted that Vera might have some knowledge of Max's strange past, as she tells Ben to keep up the good work when dealing with aliens. Ben doesn't seem to take her seriously, but her face hints that she might have been serious. This may only have been done for comedic effect, however, and thus may have no actual bearing on the story. Aunt Vera appears in the episode "Permanent Retirement".

Captain Shaw

Shaw is a fisherman. He relentlessly pursues the Krakken, a beast that roams the lake in which he fishes. Upon first seeing this creature, he swore to "capture" it (by means of a harpoon cannon) in order to verify his claims. This mission has earned him a less than favorable reputation among the nearby residents. Most think of him as crazy. Ben helps him to reveal the existence of the Krakken, but Shaw is unable to capture it. Captain Shaw appears in the episode "The Krakken".

The Galactic Enforcers

The Galactic Enforcers are a group of alien super heroes who act as law enforcement for the universe. Three of them appear in "The Galactic Enforcers" (presumably, many more would be needed for such an organization to be effective). Their leader is Ultimos, the Specimen Prime, who bears more than a passing resemblance to Superman and follows the Galactic Code of Conduct too much to the letter. Earth chocolate is poisonous to his species (It is known by another name to the Galactic enforcers, as are many common Earth chemicals). His subordinates are Synaptak, a telekinetic, flying brain with an octopus-like lower body, and Tiny, a female Tetramand.

Hoverboard

Hoverboard is one of three alien bounty hunters sent to take the Omnitrix from Ben. He is from the species Ditorian. He has nearly impenetrable gray armor, a black helmet with a small, green triangle (presumably for sight) on it, and carries a large rifle. Unlike the other hunters, Hoverboard is allied against Vilgax. After helping Ben to defeat the other hunters, he gives Ben his hoverboard, saying that it might come in handy. Hoverboard appears in the episode "Hunted" and he is mentioned in "Framed".

Krakken

The Krakken is a massive sea-creature that lives in the lake Ben visits in "The Krakken". The Krakken looks slightly similar to a Plesiosaur, possibly being an off-shoot of the species. The main differences are that it has two tentacle-like tongues, each with a mouth on the end, and large skin-flaps connecting its fore-legs to its body. The Krakken seems to be very territorial, attacking anyone who disturbs its nest.

Lt. Steel

Lt. Steel is the head of SACT which stands for Special Alien Capture Team. He has had many encounters with Kevin, who was posing as the Omnitrix aliens at the time. At first he is very suspicious of Ben and his family, but later allows them to come and go as they please.

Technorg

Technorg is a Detrovite captured by Slix Vigma to fight in gladiator games. His strength is on par with Fourarms' and he had a large metal ball in place of his left hand. After Ben spares his life, he pledges his life to Ben. Later, he distracts Kevin while Ben (as Cannon Bolt) leaves in an escape pod. Technorg appears in the episode "Grudge Match", and was last seen about to beat up Kevin as the Megacruiser blasted off for another galaxy.

Acid Breath

Acid Breath is one of Zombozo's three minions. He has the ability to breath corrosive acid, which he can project great distances for an extended amount of time. Acid Breath appears in the episode "Last Laugh".

Clancy

Clancy is a man who has the ability to control any type of insect. He lives at 8610 Chester Street, which is an abandoned apartment building. When Councilwoman Liang tried to redevelop the area and have his home torn down, he kidnapped her with the intention of feeding her to his insects. Luckily, Fourarms was there to stop him. After that plan failed, Clancy went to the nuclear power plant to cause a meltdown, which would kill everyone and everything in the city, except for the cockroaches. Clancy made himself protective suit out of cockroaches in order to survive the blast. This plan was stopped by a sick Heatblast, whose powers had reversed and gave him the ability to control cold instead of heat. Finally, he attempted to take revenge on the trio. Once again, he is stopped, this time by Max's San Ju Yen Pien cold medicine, which attracted the bugs and overrode Clancy's control over them.

Doctor Animo

Doctor Animo was once a promising researcher in veterinary science. His career was cut short when it was discovered that he was performing twisted genetic experiments on animals. He had hoped that his research would win him the Verties Award, which is an award in veterinary science. Because of the nature of his research, he lost the award to another doctor, named Kelly. This drove him mad, and he dropped off the map for five years until he could perfect his research. In the episode "Washington B.C.", he finally finishes his work.

By using the Transmodulator, a device of his own design, he could mutate animals into giant versions of themselves. The second phase of his work involved reanimating dormant cells, literally bringing dead animals back to life. All of this was in pursuit of the award which he had lost. His quest ended in failure, since Ben was there to stop him. He was arrested in that episode.

Fright Wig

Frightwig is one of Zombozo's three minions. She has pale skin, a tight-fitting body suit, and five orange tentacles for hair. The tentacles are extremely powerful, giving her strength equal to that of Thumbskull. She's also extremely quick. Frightwig appears in the episode "Last Laugh".

The Great One

The Great One is a giant, tick-like alien that travels from world to world, sucking the energy from the planets it lands on to feed itself. This process poisons and eventually destroys the worlds it visits. Its shell is nearly impenetrable and its feeding process brings the ground to life as an extra defense, making it very difficult to attack. On top of that, it is followed by a group of worshippers that want to make sure that it completes its task. The Great One was destroyed by Ben as Cannon Bolt.

Hex

Hex is a powerful magician with magical charms called the Charms of Bezel. By using the Charms of Bezel, which give him the powers of levitation, fire, reincarnation, luck, and lightning, he can cast powerful spells on whatever he chooses. He seeks an ancient spellbook called the Archamada Book of Spells. It dates back to the 16th century and contains powerful spells that, when wielded by someone holding the Charms of Bezel, give the wielder unimaginable powers. Hex appears in the episode "Lucky Girl".

Howell Waynewright

Howell Wayneright is obsessed with finding proof of alien life, so when he finds Grey Matter at a water park, he sees his ticket to fame. He inadvertently gives this ticket up when he turns Grey Matter over to The Organization, thinking that they'll help him spread the word. Instead, they decide to dissect Grey Matter and dispose of Howell. He is forced to rescue Grey Matter from them as a result. When Grey Matter reverts back to human form when Howell isn't looking, he decides to give up chasing aliens. Howell appears in the episode "A Small Problem".

Joey/Rojo 

Joey is the leader of a heavily armed female biker gang. When she tries to rob an armored truck, she is thwarted by Ben as Fourarms. The remnants of one of Vilgax's defeated drones soon fuse with Joey and becomes Rojo, a powerful cyborg. The upgrade gives her the ability to fly, super-strength, and a pair of blasters attached to each shoulder. Vilgax is able to communicate with her through the parts and force her to track down the Omnitrix for her. Joey is turned back to normal when Upgrade shorts out the spare parts. Joey appears in the episode "The Alliance".