Kat Dennings was born Katherine Litwack in Bryn Mawr, Pennsylvania, near Philadelphia, to Gerald and Ellen Litwack. She is the youngest of five children.
Kat was predominantly home-schooled, graduating at the age of 14. Her family subsequently moved to Los Angeles, California to support Kat acting full-time.
After work doing commercials, she began work in television, starting with a role on HBO's "Sex and the City" (1998), following up with roles on "Raising Dad" (2001), The Scream Team (2002) (TV), "Everwood" (2002), "Without a Trace" (2002) and "ER" (1994), among others.
Kat made the move to the big screen with supporting roles in Raise Your Voice (2004), The 40 Year Old Virgin (2005) and Big Momma's House 2 (2006). She later achieved a level of fame with roles in The House Bunny (2008) and Nick and Norah's Infinite Playlist (2008).