Gwen Tennyson (Classic)

Gwendolyn "Gwen" Tennyson is Ben Tennyson's cousin (the two share the same birthday). Throughout the original series, she constantly bickers and insults him with dry wit and sarcasm. Gwen was first introduced in "And Then There Were 10". She uses her laptop to research any strange people and/or creatures they might come across.

Original series
In the original series, Gwen shares a with Ben, insulting him with dry and most of the time, in part due to their shared birthday. She uses her laptop to research any strange people and/or creatures they might come across, and is a capable gymnast and has had some training in martial arts. She has also shown an almost innate skill in using various complicated devices or objects, such as in the "What If?" episode "Gwen 10", when Gwen gained the Omnitrix instead of Ben and proved to be far more adept in its use than he initially was.

Overall, her most notable skill is her innate, if latent, ability at magic. Having within her what Charmcaster calls a "magical aura", Gwen is capable of using various magical artifacts and spells. When using the magical, luck-giving Charm of Bezel, she was able to activate it instinctively, whereas Hex did or could not. Later on, when she takes and uses his staff, she was able to make it fire an energy blast—according to Charmcaster, only someone of Hex's skill should have that ability. Gwen starts tapping into her magical powers when she procures a book of spells from Charmcaster in the episode "A Change of Face".

On two occasions, Gwen has the Charms of Bezel to become a superhero by the name of Lucky Girl. At first, her ability drew from the "luck" Charm of Bezel, which innately gave her perfect luck. While wearing the charm, any action she took would result in a Rube Goldberg-style chain reaction benefiting her original intent, but usually injuring Ben in the process. She later brought back her superhero identity after obtaining the Keystone of Bezel, which increased her natural abilities to superhuman levels rather than just affecting her luck. Both times, Gwen was forced to retire when the Charms of Bezel were destroyed.

Ben 10: Alien Force
In the sequel series, Ben 10: Alien Force, Gwen has grown into a calm and collective teenager, and she and Ben get along much better and are no longer openly hostile towards one another. In this version, Gwen wears a plain, white shirt, loosely-buttoned blue sweater, a black skirt with black tights, her hair is much longer and darker, her eyes are much darker, and her lips are more visible. Gwen is now a black belt (taking classes in Tae Kwon Do, according to dialogue in "Simple"), but tends to favor using her powers. She is able to create energy constructs for nearly any purpose, usually creating platforms to levitate herself (and others), beams to grab enemies, circular blasts to knock enemies back, projecting beams from her eyes that seem to simulate heat vision, and opening up interdimensional portals. She also has a wide range of other loosely defined supernatural abilities, such as dowsing, limited telepathy, and clairvoyance. Her powers are revealed to be alien in origin; her grandmother, Verdona, is an energy being known as an Anodite and surprisingly she is the only descendant of hers who inherited Verdona's powers. Verdona tells Gwen that what she and others originally thought of as "magic" was actually the manipulation of mana, a substance of magic - making Anodites a magic-wielding race. Verdona offers to take Gwen to her home planet and train her in the mystical ways of the Anodites, but Gwen prefers to remain on Earth with Ben and Kevin. She hates being called an "energy being", referring to her Anodite heritage. In the episode "In Charm's Way", it's implied that humans like Charmcaster can also be trained to utilize mana.

In the episode "Unearthed", an alien creature is able to see her as an Anodite, in which she looks exactly like her grandmother's true form, but slightly shorter. In "War of the Worlds", when Kevin was threatened by a Highbreed commander, she assumes her Anodite form for the first time and easily defeated the commander. She was almost overwhelmed by her own power before Kevin snaps her out of it.

During the course of the series she has developed a romantic relationship with Kevin. They have also been shown to have arguments, usually starting with Gwen always trying to force Kevin to "ask her out" and him always answering "don't push me". In the episode, "Fool's Gold" Kevin appears to be avoiding her because he is ashamed of his recent mutation due to accidentally absorbing a massive feedback pulse as a result of trying to hack the Omnitrix. He gives her a locket of he and Gwen when he was in human form, asking her to remember him as he was. Gwen says she doesn't care what he looks like, and he replies "But I do."

In the season three premiere, Gwen has altered her wardrobe, gaining a red shirt, a black vest with gray pants, and a ponytail. Ben and Gwen seem to have revived their infamous rivalry from the original series, in part due to Ben's cockiness and inflated ego; in the third season, Gwen pours a smoothie over Ben's head, and he nearly returns the favor. Despite their rivalry, they both still have a strong bond, visible in In Charm's Way, when Ben defends Gwen and informs Kevin that she has been spending all of her spare time in order to find a cure for Kevin's condition. It is shown in both "Vengeance of Vilgax" and "Inferno", respectively, that Gwen suffers from both arachnophobia and claustrophobia.

Energy Manipulation


Given her Anodite lineage, Gwen is capable of energy manipulation. She also has a wide range of other loosely defined magical abilities, such as dowsing, telepathy and clairvoyance.

Her powers are revealed to be alien in origin; her grandmother, Verdona, is an energy being known as an Anodite. Verdona tells Gwen that what she and others originally thought of as "magic" was actually the manipulation of a Force-like energy called mana. Verdona offers to take Gwen to her home planet and train her in the mystical ways of the Anodites, but Gwen prefers to remain on Earth with Ben and Kevin. She hates being called an "Energy being", referring to her Anodite heritage. In 'War of The Worlds', Gwen releases her Anodite form, and was almost overwhelmed by her own power before Kevin snaps her out of it. Gwen can also conjure up dimensional vortexes, stepping stones, energy blastes, levitation,shields

"Magic"


In the original series, Gwen's powers first manifested in the form of what she originally believed to be "magic", thus enabling her to use various magical artifacts and spells (see Gwen's Spells). When using the magical, luck-giving Charm of Bezel, she was able to activate it instinctively, whereas Hex did or could not. Later on, when she takes and uses his staff, she was able to make it fire an energy blast—according to Charmcaster, only someone of Hex's skill should have that power. Gwen starts tapping into her magical powers when she procures a book of spells from Charmcaster in the episode "A Change of Face".

On two occasions, Gwen used the Charms of Bezel to become a superheroine by the name of Lucky Girl. At first, her ability drew from the "luck" Charm of Bezel, which innately gave her perfect luck. While wearing the charm, any action she took would result in an Rube Goldberg-style chain reaction benefiting her original intent, but usually injuring Ben in the process. She later brought back her superhero identity after obtaining the Keystone of Bezel, which increased her natural abilities to superhuman levels rather than just affecting her luck. Both times, Gwen was forced to retire when the Charms of Bezel were destroyed.

In Alien Force, despite Gwen's current preference for direct forms of mana manipulation, she is still able to use "magic" in the more traditional sense. Gwen mentions to both Charmcaster and Kevin in In Charm's Way that she still has Charmcaster's old spellbook, and is currently looking through it constantly to find a cure for Kevin's mutation.

Athletics


Gwen is a capable gymnast and has had some training in martial arts. At the age of fifteen it is revealed that she has already received a black belt in karate and has even started teaching Ben.

Intelligence
Gwen is shown to be quite intelligent and knowlegdeable (if more so than Ben). Before discovering her powers she would often use her "brains" to help Ben. She is shown to be a bit of computer/tech wiz as well.

Trivia

 * In the original series, Gwen is voiced by Meagan Smith.
 * In Ben 10: Alien Force, Gwen is voiced by Ashley Johnson.
 * In the episodes "Ben 10,000" and "Ken 10", Gwen is voiced by Tara Strong. Incidentally, Strong also voices the 10-year-old Ben.
 * She could be Ben's future wife instead of Kai or Julie, since the future shown in "Ken 10" & "Ben 10,000" was just an alternate future/timeline.
 * In the live-action movie, Ben 10: Race Against Time, Gwen was played by Haley Ramm.
 * Gwen's magical abilities and even her name might have been inspired by the Sibyls from Chris 'D Lacey's series of books,The Last Dragon Chronicles. In the series, Sibyls are able to command the supernatural, and they are the descendants of a powerful magics user, Gwendolen.
 * Gwen`s lucky girl suit looks similar to Hellcat from Marvel.
 * The Cat logo on Gwen in the first series looks very similar to Sly Cooper's logo.