The Tennysons •
Benjamin Kirby "Ben" Tennyson (voiced by
Tara Strong): :Ben is a confident and occasionally immature boy who enjoys attention and often makes jokes, even in tense situations. Despite his impulsive behavior, he is good-hearted, loyal, and motivated by a genuine desire to help others. Ben is highly protective of his family and is willing to risk his safety to defend anyone in danger. Though playful by nature, he demonstrates intelligence, adaptability, and an eidetic memory, often relying on his quick thinking to overcome challenges when his usual means fall short. Ben's catchphrases include "It's Hero Time!" and "Goin' Hero!". •
Gwendolyn "Gwen" Tennyson (voiced by Meagan Smith): :Gwen is Ben's cousin and is depicted as a kind and intelligent girl, very skilled with computers and possessing a level of martial arts skills. She is also very independent but is very organized, sometimes to the point of compulsive, but can be a light-hearted schemer and immature as Ben. Overall, her most notable skill is her innate, if latent, ability at magic, first shown in "Tough Luck" when she was able to use Hex's staff, which can only be used by a master magician, to defeat Charmcaster. She later obtains Charmcaster's spellbook in "Change of Face" and begins improving her magic. • Magister Maxwell "Max" Tennyson (voiced by
Paul Eiding): :Ben and Gwen's grandfather, who takes the two on a cross-country road trip for Summer vacation. In "Truth", Max reveals he was a part of an intergalactic secret agency known as "The Plumbers" and handled many extraterrestrial encounters in the past. His history as a Plumber has given him knowledge, training, and equipment for fighting aliens as well as an unconventional taste in food, much to the dismay of his grandchildren. In "The Visitor," an old alien acquaintance of Max's called Xylene reveals that Max was the intended recipient of the Omnitrix.
Antagonists • Vilgax (voiced by
Steve Blum) – A Chimera Sui Generis
warlord regarded as one of the most feared aliens in the galaxy. His primary goal in the show is to obtain the Omnitrix, which he wishes to use in order to create an army of soldiers who can transform at his command. Vilgax is revealed to have crossed paths with Max, having faced Max before. For the majority of the first season, Vilgax was injured and remained in a regeneration chamber until the season finale. Once healed, he was cybernetically enhanced, giving him colossal size, strength and durability that made him a match for every alien Ben could access at that time. Vilgax was the main antagonist of the first season and second season, a recurring antagonist in third season and the main antagonist in the final episode of the fourth season. • Dr. Animo (voiced by
Dwight Schultz) – A promising
veterinary scientist whose career was cut short when he was discovered performing twisted genetic experiments on mutating animals. He had hoped that his research would win him the Verties Award. Because of the nature of his research, he lost the award to another doctor named Kelly. This drove him insane, and he dropped off the map for five years until he could perfect his research. After being defeated by Ben for the first time, Dr. Animo makes himself a personal nemesis to the boy, always hoping to defeat him and rule the world. His powers include controlling mutant animals, reviving them and creating them. He is Ben's tertiary archenemy. • Kevin 11 (voiced by
Michael Reisz in Season 1; by
Charlie Schlatter in Seasons 2–4) – An 11-year-old
delinquent sociopath with powers that allow him to absorb energy. He uses the ability to commit crimes to benefit himself. He initially seeks to team up with Ben to become unstoppable, but after Ben refuses, he absorbs power from the Omnitrix instead. This transformation drives him to cause chaos and serve as a recurring adversary to Ben, earning him the nickname “Kevin 11.” • Zs'Skayr (voiced by
Steve Blum)– An Ectonurite
high king whose rule over the Anur
star system saw an opportunity to expand when he learned of the Omnitrix from one of Vilgax's crash-landed data probes. Searching the galaxy, he tried to sample Flourauna DNA into the Omnitrix but ended up having his own DNA sampled along with it, becoming the genetic donor of Ghostfreak. His powers include invisibility, intangibility, possession, tentacles, energy beam projection, telekinesis and firing energy beams from his hands. He was a minor antagonist in the second season and the main antagonist of the third season. • Doctor Viktor (voiced by
Michael Dorn) - An alien resembling Frankenstein's monster who is Zs'Skayr's second in command and oversees his master's plan during Season 3. While trying to stop Ben from interfering with their plan, Viktor accidentally opens a portal to the Null Void and is sucked in. • The Werewolf - A werewolf-like alien who serves Zs'Skayr and gathers satellite equipment for his master's plan. When the Tennysons' interference causes the satellite equipment gather to explode, the Werewolf is caught in the blast. • The Mummy - A mummy-like alien who serves Zs'Skayr, gathering a dangerous energy crystal with mutagenic properties called Corrodium. When Viktor opens a portal to the Null Void, the Mummy is sucked in along with him. • The Forever Knights – A secret British
paramilitary organization formed during the Middle Ages and evolved into an international syndicate that first came to the United States in the 1920s. • Enoch (voiced by
Richard Doyle) – One of the leaders of the Forever Knights, though he mostly works behind the scenes and rarely directly battles the Tennysons. At the end of "Perfect Day" he becomes trapped in his own dream machine and is replaced by the Forever King. • Driscoll / Forever King (voiced by Richard Doyle) – A former Plumber disgraced after being caught stealing technologies from alien criminals for personal gain, who joined the Forever Knights and eventually became their leader with the goal of achieving world domination. After learning of the Plumbers' secret "sub-energy" weapon the Forever King assembles the Negative 10, a team of the Tennysons' human enemies, to steal it to achieve his goal. He was the main antagonist of season four. • Hex (voiced by
Khary Payton; by Kari Wahlgren as a child)– A self-proclaimed master
magician and sorcerer from the inter-dimensional world of Ledgerdomain. • Charmcaster (voiced by
Kari Wahlgren)– Hex's gifted 15-year-old niece, who initially appears loyal to her uncle, Hex, but is later revealed to have been using him to pursue power for herself. She later attempts to use a spell to swap bodies with Ben in order to gain possession of the Omnitrix, but accidentally switches bodies with Gwen instead. The plan ultimately fails, and Gwen steals her spellbook. Charmcaster later joins the Negative 10 to seek revenge on the Tennysons, though her primary grudge is against Gwen. Her abilities include mana manipulation and spellcasting. She primarily serves as Gwen’s archenemy. ==Voice cast==