|Age|| 10 (Ben 10)|
11 (Omniverse flashbacks)
|Affiliations|| Tennyson Family|
|Powers and Abilities|
|Relatives|| Camille Mann-Tennyson (cousin)|
Mr. Mann (uncle)
Mrs. Mann (aunt)
Joel Tennyson (cousin-in-law)
Ben Tennyson (cousin-in-law)
Gwen Tennyson (cousin-in-law)
|Voice Actor||Tara Strong|
|First Appearance||Big Fat Alien Wedding|
Like Camille and Camille's parents, Lucy is a Lenopan. She is at this moment, Joel Tennyson's cousin-in-law, and was one of the few Lenopans not to be involved in the sabotage of the marriage. In Omniverse, Lucy is now a Plumber.
Lucy is a very upbeat and mischievous girl, who loves playing pranks on people, as she especially enjoys teasing her cousin Gwen. She's very silly, but is also apparently quite competent, seeing as how she managed to get through Plumbers' Training Academy in a relatively short amount of time.
In the original series, Lucy has long blonde hair with blue eyes. She is shown wearing a black sleeveless shirt with a star on it, along with a red skirt. She also has two distinct whisker marks on her face.
In Omniverse, 11 year old Lucy's skin is more pink, the whisker like marks on her face are gone, with freckles taking their place. Her eyes have changed color, becoming purple.
16 year old Lucy wears a black sleeved dress, with a red collar, a star on the chest area, white socks that go over her knees, red shoes and red lipstick. She wears her hair in a ponytail.
Lucy's 10 year old Lenopan form was not shown.
Lucy has two different Lenopan forms: her more natural one, lacking legs, with larger head tendrils, and less human facial features, and her humanoid form, which is smaller, has legs, and a more human like face with mud flowing around her head, resembling hair.
- Big Fat Alien Wedding (first appearance)
Ben 10: Omniverse
- Mud is Thicker than Water (first re-appearance; past and present)
- According to Matt Wayne, Lucy's eyes went from being blue to purple because she's modeled her human look after Elizabeth Taylor, whose eyes were either blue or violet, depending on the light.
- Lucy bears a striking resemblance to a younger Cassie Sandsmark (aka Wonder Girl) from DC comics due to her blonde hair and her shirt, which was one of Cassie's first costumes.
- The whisker marks on her face give Lucy a striking resemblance to the female illusion form of Naruto, from the popular anime series of the same name.
- Due to her age, Lucy was never involved with the Plumbers/Lenopan feud and appears to have no problem with Joel and Camille's marriage.
- Lucy is the youngest Lenopan to appear in the series.
- Lucy's Lenopan abilities aren't shown until the end of Big Fat Alien Wedding, when Ben trips on Lucy's "feet" while they were dancing at the wedding
- In Mud is Thicker than Water, It is revealed that she is the first ever Lenopan to be a Plumber.
- According to Ben, Lucy is Gwen and Ben's "Grandpa Max's brother's son's wife's mother's sister's daughter", or simply, their cousin.
- According to Derrick J. Wyatt, Lucy likes pottery, and anything having to do with mud or clay.