Gwendolyn "Gwen" Tennyson is a Human/Anodite hybrid Plumber, the paternal first-cousin of Ben Tennyson, and (along with Kevin Levin and Rook Blonko) a frontline member of his team. Gwen was first introduced when her parents send her on a summer-long road trip with her Grandpa Maxand her cousin Ben.
She has, as Verdona refers to it, "The Spark".
In the original series, Gwen had short red hair held by a blue hair clip and green eyes. As she has grown older, her red hair has grown longer and her eyes have darkened.
In the series Ben 10, Gwen wore a blue shirt with a cat logo on her chest and white pants. She wears a blue hairclip in her bangs. Her lucky girl outfit is worn in Tough Luck andLucky Girl. 11 year old Gwen in Omniverse looks just like she did in the original series except that she has freckles.