For her first day on the ''ER'' set, Linda Cardellini wanted to hit the ground running. Instead, she just hit the ground. ''I was supposed to rush into admitting, and I had some soundproofing on my shoes and took a spill,'' says Cardellini, who joins the NBC drama's cast as single-mom nurse Samantha Taggart on Oct. 30. ''After that, I realized I had made as big a fool of myself as I possibly could, so there's nothing to be afraid of.''
Unless she's scared Taggart will get swept off her feet by Dr. Luka Kovac (Goran Visnjic). Since giving birth to a son in her teens, the nurse ''hasn't really let men into the picture, and it becomes obvious that my son is really craving that,'' explains Cardellini, who's signed for a two-year stint. ''That brings Luka and Samantha closer.''
The actress also finds new romance as Velma Dinkley (whose nasal catchphrase ''Jinkies!'' Cardellini defines as ''an exclamatory version of 'Goodness!''') in this spring's ''Scooby-Doo 2: Monsters Unleashed.'' ''She's very uncomfortable with intimacy,'' Cardellini says of the superdweeb, who'll develop a crush on a criminology-museum curator (Seth Green). ''In many ways, she's intelligent, but when it comes to romantic skills, she's a little behind.''
Getting cast as a brainiac wasn't a new experience for Cardellini. For cult-TV enthusiasts, she's best known as reluctant ''math-lete'' Lindsay Weir in NBC's beloved 1999-2000 dramedy ''Freaks and Geeks.'' Although she was 24 at the time, she had no trouble getting back into the adolescent mind-set. ''Maybe it should have been [difficult],'' says Cardellini, who still dates ''Freaks'' costar Jason Segel. ''But sometimes Hollywood feels like a big high school.''
In fact, ''ER'''s Nurse Taggart marks Cardellini's most mature role to date. ''I was used to playing people who were going through growing pains as they came into womanhood,'' she says. ''Samantha was brought into womanhood at a very young age when she became a mother.''
The Redwood City, Calif., native first attracted attention as a teenage temptress who nearly broke up Cory (Ben Savage) and Topanga (Danielle Fishel) on the kid-com ''Boy Meets World.'' ''I was at my old elementary school, and this group of 8-year-olds ran up to me and called me a 'home wrecker,''' recalls Cardellini. ''And I thought, My God, how do they know what 'home wrecker' means?'' Jinkies!