Karen is a co-worker of Jim's at the Stanford branch.
Before Jim arrived, Karen was a likely candidate for the position of Assistant Regional Manager.
At first, she doesn't think Jim fits in there and dislikes the way he looks at the camera, but eventually she grows to like him, apparently developing a crush on him.
After their job interviews in New York, Jim leaves Karen in New York City and returns to Scranton to ask Pam out for dinner.
In The Office Summer Vacation clip released early September Karen states that "Jim dumped my ass and left me crying by a fountain in New York".
After returning from New York, Karen explains to Jim that she has worked too hard for her career and does not intend on leaving.
However, the next day, she is not at the office and her desk is empty.
Karen is currently the Regional Manager of Dunder Mifflin Utica. It was revealed that it was really a plot by Stanley to get more money.(Branch Wars) Karen is pregnant.
Jim is not the father after much speculation by Michael. Karen asks Pam how Jim is doing and Pam tells her that she and Jim are engaged and Karen seemed genuinely happy for her.(Lecture Circuit Part 1) She makes a cameo appearance during the season finale, "Company Picnic".
Karen appeared in Michael's movie "Threat Level Midnight".
In it she appeared as a girl at a bachlorette party and flirts with Michael in it.
Karen is later interviewed about it and asks the cameras why they are singling her out.
In the movie, she also participates in "The Scarn", a crazy dance involved in the film with the rest of the people in the scene.
(Rhetorical question — you do.) Fortunately, the release of his new film Admission has revealed the quickest way to Rudd's heart: All you have to do is appear in an NBC Thursday night sitcom — easy enough!