Basics

Gretchen is one of the Plastics, and possibly Regina's closest friend (or at least a confidante). She is very wealthy because her father invented Toaster Strudel . Partially as a result of Cady, Janis and Damian's scheme, she begins to crack, spilling many of Regina's deepest secrets to Cady in anger at being treated badly by her friend. Throughout the film, she likes Jason, a flirtatious pervert. In senior year, she dyes, lengthens and straightens her hair, learns Vietnamese and hangs out with the "cool Asians", so she can be a new "Queen Bee". Throughout the movie, Gretchen tries to make "fetch" the new slang word for cool.
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