Jennifer "Jen" Larkin is Andy's sister who attends the same school. A perfect target for Andy's pranks. With her attractive looks and intelligence, she is very active and popular at school. A strong participant, competitor and winner at many things- science fairs, cheerleading (she's the captain), student council, etc. The only stain on her shiny plate is... of course, her brother, who she sees as a pest. Andy also tends to see her as a pest. She is the part of the gymnastic team and student body president. Also has a crush on the captain of the football team, Craig.
She is a normal 17 year old girl who gets annoyed with her brother's pranks like her parents and the community and gets angry whenever he does something to embarrass her. Jen does what ever she can to ruin her brother's pranks so he can get caught and be punished and save her reputation as well as see her brother pay for his pranks.
Despite that she hates her brother's pranking nature, at times they would get along and work together when they are in trouble and she would depend on her brother's pranking, like in the episode "Stone Cold" she and Andy work together to win the curling competition but when their competitor see's that they've cheated, Andy manages to frame them and get him and Jen out of trouble.
Like her mother, if people criticize her brother saying something is wrong with him, she would get offended, while people usually call him a dork and dweeb like she usually does, she doesn't let anyone insult her brother on that degree.
She is slim, with red curly hair, a purple blouse and white pants. In the episode Weight to Go, Andy, she had something similar to anorexia. She is also a bit of a neat freak.