EXCLUSIVE: Kate Walsh is about to get scary – Scary Movie 5 that is. The Private Practice star has signed up to do a cameo in the latest installment of the mock horror franchise. She joins the just named Heather Locklear and Molly Shannon in the movie. Malcolm Lee is directing Scary Movie 5 from a script by David Zucker, who wrote and directed 2003’s Scary Movie 3 and 2006’s Scary Movie 4. Besides her Dr. Addison Montgomery role on the ABC series, Walsh appears in The Perks of Being A Wallflower as the mother of Logan Lerman’s Charlie character. Paul Rudd and Dylan McDermott co-star along with Emma Watson and Ezra Miller. The coming-of-age movie debuts this weekend at the Toronto International Film Festival and opens on September 27. Walsh is repped by CAA and Evolution Entertainment.