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), 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).
Kat continues to act in feature films and is an avid video blogger. Since 2011, she has starred with Beth Behrs in the CBS television series 2 Broke Girls (2011).
- Partiya dlya chempionki (TV Mini-Series) - 2014
In the protagonist of Julia
- Pyataya strazha (TV Series) - 2013
In the protagonist of Violetta