Inspired by her older sister, Aimée (with whom she would team in "Big Wolf on Campus"), Maggie Castle began acting in Montreal children's theater when she was four years old. She made her screen debut as Nina Petronzio's sister in the 1990 Van Gogh fantasy "Vincent et moi," which she followed by playing Heather Mathieson's daughter in the prodigal slacker comedy "Because Why" and one of the Dionne quintuplets in the miniseries "Million Dollar Babies." Over the next few years, Castle alternated between guest slots in TV shows like "Goosebumps," "Are You Afraid of the Dark?," and "Vampire High," and roles in family movies like "Kids of the Round Table," "Nico the Unicorn," and "Babel" and such grown-up fare as "The Jackal," in which she played a teenage hostage opposite Bruce Willis and Richard Gere. In 2001, Castle landed her first lead, in Jay Baruchel's religious revenge short, "Edgar and Jane," after which it was back to minor roles in the ensemble comedies "Fast Food High," "The Perfect Man," and "The House." Allan Moyle's 2007 black romp "Weirdsville" seemed to change Castle's fortunes, however, as she was menaced by zombies in "The Mad," coped with unemployed Easter bunnies in "Hank and Mike," and offered sisterly support to Rachel McAdams in "The Time Traveler's Wife." Since co-starring in Disney's celebrity comedy "StarStruck," Castle has become a fixture on two TV series, as the voice of Molly MacDonald in "Arthur" and as feisty Jenny Kolinsky in "Todd and the Book of Pure Evil."