Heather Cristina Matarazzo (born November 10, 1982) is an American actress who played Lilly Moscovitz in the 2001 disney comedy film The Princess Diaries and its 2004 sequel, The Princess Diaries 2: Royal Engagement. She also played Joan Paulson in the Grey's Anatomy episodes Time Stops and You're My Home and Katie in the 2002 Touchstone Pictures film Sorority Boys.